Android java: gradle corrupted, how to fix it

This is error message when gradle corrupted due to accidentally deleted or fail updated.

"The contents of the immutable workspace '~/.gradle/caches/9.1.0/groovy-dsl/52b1078aa736f3877f522d2046a7f837' have been modified" 

To make easier to fix gradle, exit Android Studio, open shell and go to project root directory. You will find file gradlew.

Clean up your gradle

$ ./gradlew --stop
Stopping Daemon(s)
2 Daemons stopped
$ rm -rf ~/.gradle/caches/9.1.0/

Run help to force gradlew download and rebuild library required.

$ ./gradlew help
Starting a Gradle Daemon, 2 stopped Daemons could not be reused, use --status for details

> Configure project :app
WARNING: The option setting 'android.usesSdkInManifest.disallowed=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.sdk.defaultTargetSdkToCompileSdkIfUnset=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.enableAppCompileTimeRClass=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.builtInKotlin=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.newDsl=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.r8.optimizedResourceShrinking=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.defaults.buildfeatures.resvalues=true' is deprecated.
The current default is 'false'.
It will be removed in version 10.0 of the Android Gradle plugin.
w: file://~/Workspace/Android/WredaContactBackup/app/build.gradle.kts:5:1: 'fun Project.android(configure: Action<BaseAppModuleExtension>): Unit' is deprecated. Replaced by com.android.build.api.dsl.ApplicationExtension.
This class is not used for the public extensions in AGP when android.newDsl=true, which is the default in AGP 9.0, and will be removed in AGP 10.0.
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties

> Task :help

Welcome to Gradle 9.1.0.

To run a build, run gradlew <task> ...

To see a list of available tasks, run gradlew tasks

To see more detail about a task, run gradlew help --task <task>

To see a list of command-line options, run gradlew --help

For more detail on using Gradle, see https://docs.gradle.org/9.1.0/userguide/command_line_interface.html

For troubleshooting, visit https://help.gradle.org

BUILD SUCCESSFUL in 28s
1 actionable task: 1 executed
Consider enabling configuration cache to speed up this build: https://docs.gradle.org/9.1.0/userguide/configuration_cache_enabling.html

Open your Android Studio, repair android studio project choose index repair.

If this error occurred

"Ambiguous method call: both 'FragmentActivity.onCreate(Bundle) (In ~/.gradle/caches/9.1.0/transforms/dae60150ff0476652c6b13819aa96f10/transformed/fragment-1.5.4/jars/classes.jar!/androidx/fragment/app/FragmentActivity.class)' and 'ComponentActivity.onCreate(Bundle) (In ~/.gradle/caches/9.1.0/transforms/48c7a661e0aa50fff79a603bd45cc34c/transformed/activity-1.12.2/jars/classes.jar!/androidx/activity/ComponentActivity.class)' match"

Invalidate cache (everything) and restart.

If you find some deprecated gradle option like these:

$ ./gradlew help
Starting a Gradle Daemon, 1 incompatible and 1 stopped Daemons could not be reused, use --status for details

> Configure project :app
WARNING: The option setting 'android.usesSdkInManifest.disallowed=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.sdk.defaultTargetSdkToCompileSdkIfUnset=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.enableAppCompileTimeRClass=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.builtInKotlin=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.newDsl=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.r8.optimizedResourceShrinking=false' is deprecated.
The current default is 'true'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The option setting 'android.defaults.buildfeatures.resvalues=true' is deprecated.
The current default is 'false'.
It will be removed in version 10.0 of the Android Gradle plugin.
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties
WARNING: The property android.dependency.excludeLibraryComponentsFromConstraints improves project import performance for very large projects. It should be enabled to improve performance.
To suppress this warning, add android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false to gradle.properties

> Task :help

Welcome to Gradle 9.1.0.

To run a build, run gradlew <task> ...

To see a list of available tasks, run gradlew tasks

To see more detail about a task, run gradlew help --task <task>

To see a list of command-line options, run gradlew --help

For more detail on using Gradle, see https://docs.gradle.org/9.1.0/userguide/command_line_interface.html

For troubleshooting, visit https://help.gradle.org

BUILD SUCCESSFUL in 5s
1 actionable task: 1 executed
Consider enabling configuration cache to speed up this build: https://docs.gradle.org/9.1.0/userguide/configuration_cache_enabling.html

Edit file gradle.properties, find those configuration and take some adjustment. You can close Android Studio and back to shell, this is my gradle.properties:

# Project-wide Gradle settings.
# IDE (e.g. Android Studio) users:
# Gradle settings configured through the IDE *will override*
# any settings specified in this file.
# For more details on how to configure your build environment visit
# http://www.gradle.org/docs/current/userguide/build_environment.html
# Specifies the JVM arguments used for the daemon process.
# The setting is particularly useful for tweaking memory settings.
org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
# When configured, Gradle will run in incubating parallel mode.
# This option should only be used with decoupled projects. For more details, visit
# https://developer.android.com/r/tools/gradle-multi-project-decoupled-projects
# org.gradle.parallel=true
# AndroidX package structure to make it clearer which packages are bundled with the
# Android operating system, and which are packaged with your app's APK
# https://developer.android.com/topic/libraries/support-library/androidx-rn
android.useAndroidX=true
# Enables namespacing of each library's R class so that its R class includes only the
# resources declared in the library itself and none from the library's dependencies,
# thereby reducing the size of the R class for that library
android.nonTransitiveRClass=true
#android.defaults.buildfeatures.resvalues=true #deprecated
#android.sdk.defaultTargetSdkToCompileSdkIfUnset=false #deprecated
#android.enableAppCompileTimeRClass=false #deprecated
#android.usesSdkInManifest.disallowed=false #deprecated
android.uniquePackageNames=false
android.dependency.useConstraints=true
android.r8.strictFullModeForKeepRules=false
#android.r8.optimizedResourceShrinking=false #deprecated
#android.builtInKotlin=false #deprecated
#android.newDsl=false #deprecated
# edited dedetok
#android.enableJetifier=true
android.generateSyncIssueWhenLibraryConstraintsAreEnabled=false

Validate gradle is clear

$ ./gradlew help

> Task :help

Welcome to Gradle 9.1.0.

To run a build, run gradlew <task> ...

To see a list of available tasks, run gradlew tasks

To see more detail about a task, run gradlew help --task <task>

To see a list of command-line options, run gradlew --help

For more detail on using Gradle, see https://docs.gradle.org/9.1.0/userguide/command_line_interface.html

For troubleshooting, visit https://help.gradle.org

BUILD SUCCESSFUL in 503ms
1 actionable task: 1 executed
Consider enabling configuration cache to speed up this build: https://docs.gradle.org/9.1.0/userguide/configuration_cache_enabling.html

Now you have clean project.  

Android java: dealing with Trusted credentials on Android 7.1.1 below for letencrypt

Dealing with connection to https on old android may depend on Trusted credentials on the the device. 

Letsencrypt root certificate does not installed on Trusted credentials prior android 7.1.1.

Some application may throw:

java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.


Solution 1 add user Trusted credentials 

Install Letsencrypt pem manually on old phone i.e android version 7.1.1 or older. You can download from https://letsencrypt.org/certs/isrgrootx1.pem?hl=en-US .

On your device (mine is evercoss gen pro x pro android 7.0). Go to setting -> Security.

You may find:

• Trusted Credentials 
• User Credentials
• Install from SD Card

Choose "Install from SD Card":

• Filed Name of Certification e.g ISGR ROOT X1 or Letsecrypt.
• Credentials Use select VPN and aps

Open your Android Studio project and create res/xml/network_security_config.xml.

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config>
        <trust-anchors>
            <certificates src="system" />
            <certificates src="user" />
        </trust-anchors>
    </base-config>
</network-security-config>

Edit AndroidManifest.xml

...
   <application
    ... 
   android:networkSecurityConfig="@xml/network_security_config"
   ...
   >
...

If https server ever falls back to http (not https), you should add cleartextTrafficPermitted="true" to the <base-config> tag (Not Recommended except your application need to access http):

...
<base-config 
   ...
   cleartextTrafficPermitted="true"
   ...
>
...

if this XML fix doesn't work, it's not the certificate—it's the Android 7.0 Cipher bug. In that specific case, you will have to use Conscrypt library (Solution 2).

Solution 2 using Conscript Library

Add dependency into gradle.build app

dependencies {
    ...
    implementation 'org.conscrypt:conscrypt-android:2.5.2'
    ...
}

Initialize at application startup or foreground

...
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N_MR1) { 
    // Below Android 7.1.1
    Security.insertProviderAt(Conscrypt.newProvider(), 1);
}
...

Android java: input events processing (collection)

There 2 ways to handle input events from user input

1. Immediate: using listener
2. At process: at the end to process data, usually user fire "process" button 

TimePicker

1. Immediate 

...
        //on view created
        // date picker
        TimePicker myTimePicker = view.findViewById(R.id.my_time_picker);
        myTimePicker.setOnTimeChangedListener(timeChangeListener);
...
    // TimePicker Listeneer
    private final TimePicker.OnTimeChangedListener timeChangeListener =
            new TimePicker.OnTimeChangedListener() {
        @Override
        public void onTimeChanged(TimePicker view, int hourOfDay, int minute) {
            // TODO
        }
    };

2.  At process

    // Pull the values exactly as they are right now
    int hour = timePicker.getHour();
    int minute = timePicker.getMinute();

RadioGroup

1. Immediate

...
        //on view created
        // date picker
        RadioGroup radioSelectModeBackup = view.findViewById(R.id.radio_select_mode_backup);
        radioSelectModeBackup.setOnCheckedChangeListener(radioListener);
...
    // RadioGroup Listener
    RadioGroup.OnCheckedChangeListener radioListener = new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(@NonNull RadioGroup radioGroup, int idSelected) {
            if (idSelected==R.id.radio_weekly) {
                // weekly
            } else if (idSelected==R.id.radio_moonthly) {
                // monthly
            }
        }
    };

2. At process 

    // Inside your "Save" or "Submit" button click listener
    int selectedId = radioSelectModeBackup.getCheckedRadioButtonId();

    if (selectedId == R.id.radio_weekly) {
        // Logic for weekly backup
    } else if (selectedId == R.id.radio_moonthly) {
        // Logic for monthly backup
    } else {
        // Nothing is selected (returns -1 if no default is set in XML)
    }

 

 

 

 

Java: using build tool gradle wrapper to setup project and run

 

• java application openjdk 17
• gradle 8.7

install gradle 

# apt-get install gradle 


create folder project example

$ mkdir example
$ cd example

create init project

wrap gradle version for your project 

$ gradle wrapper --gradle-version 8.7
openjdk version "17.0.16" 2025-07-15
OpenJDK Runtime Environment (build 17.0.16+8-Debian-1deb12u1)
OpenJDK 64-Bit Server VM (build 17.0.16+8-Debian-1deb12u1, mixed mode, sharing)

init using gradle 8.7  debian 13 uses old 4.4 

$ ./gradlew init \
  --type java-application \
  --dsl groovy \
  --test-framework junit-jupiter \
  --package com.dedetok \
  --project-name example
openjdk version "17.0.16" 2025-07-15
OpenJDK Runtime Environment (build 17.0.16+8-Debian-1deb12u1)
OpenJDK 64-Bit Server VM (build 17.0.16+8-Debian-1deb12u1, mixed mode, sharing)
Downloading https://services.gradle.org/distributions/gradle-8.7-bin.zip
...............................................................................................................................
Unzipping ~/.gradle/wrapper/dists/gradle-8.7-bin/bhs2wmbdwecv87pi65oeuq5iu/gradle-8.7-bin.zip to ~/.gradle/wrapper/dists/gradle-8.7-bin/bhs2wmbdwecv87pi65oeuq5iu
Set executable permissions for: ~/.gradle/wrapper/dists/gradle-8.7-bin/bhs2wmbdwecv87pi65oeuq5iu/gradle-8.7/bin/gradle

Welcome to Gradle 8.7!

Here are the highlights of this release:
 - Compiling and testing with Java 22
 - Cacheable Groovy script compilation
 - New methods in lazy collection properties

For more details see https://docs.gradle.org/8.7/release-notes.html

Starting a Gradle Daemon, 1 incompatible Daemon could not be reused, use --status for details

Enter target Java version (min: 7, default: 21): 17

Select application structure:
  1: Single application project
  2: Application and library project
Enter selection (default: Single application project) [1..2] 1

Generate build using new APIs and behavior (some features may change in the next minor release)? (default: no) [yes, no] no


> Task :init
To learn more about Gradle by exploring our Samples at https://docs.gradle.org/8.7/samples/sample_building_java_applications_multi_project.html

BUILD SUCCESSFUL in 5m 12s
1 actionable task: 1 executed

./settings.gradle

plugins {
    // Apply the foojay-resolver plugin to allow automatic download of JDKs
    id 'org.gradle.toolchains.foojay-resolver-convention' version '0.8.0'
}

rootProject.name = 'example'
include('app')

./app/build.gradle

plugins {
    // Apply the application plugin to add support for building a CLI application in Java.
    id 'application'
}

repositories {
    // Use Maven Central for resolving dependencies.
    mavenCentral()
}

dependencies {
    // Use JUnit Jupiter for testing.
    testImplementation libs.junit.jupiter

    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'

    // This dependency is used by the application.
    implementation libs.guava
}

// Apply a specific Java toolchain to ease working on different environments.
java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

application {
    // Define the main class for the application.
    mainClass = 'com.dedetok.App'
}

tasks.named('test') {
    // Use JUnit Platform for unit tests.
    useJUnitPlatform()
}

./gradle/libs.versions.toml

[versions]
guava = "32.1.3-jre"
junit-jupiter = "5.10.1"

[libraries]
guava = { module = "com.google.guava:guava", version.ref = "guava" }
junit-jupiter = { module = "org.junit.jupiter:junit-jupiter", version.ref = "junit-jupiter" }

To show current gradle version

$ ./gradlew --version

------------------------------------------------------------
Gradle 8.7
------------------------------------------------------------

Build time:   2024-03-22 15:52:46 UTC
Revision:     650af14d7653aa949fce5e886e685efc9cf97c10

Kotlin:       1.9.22
Groovy:       3.0.17
Ant:          Apache Ant(TM) version 1.10.13 compiled on January 4 2023
JVM:          17.0.16 (Debian 17.0.16+8-Debian-1deb12u1)
OS:           Linux 6.12.57+deb13-amd64 amd64

Test run

$ ./gradlew run
Path for java installation '/usr/lib/jvm/openjdk-17' (Common Linux Locations) does not contain a java executable

> Task :app:run
Hello World!

BUILD SUCCESSFUL in 473ms
2 actionable tasks: 1 executed, 1 up-to-date

or you can run using style $ ./gradlew :app:run

Now add maridb jcoonect into project, using Traditional Groovy Approach. edit ./app/build.gradle

...
dependencies {
    // Use JUnit Jupiter for testing.
    testImplementation libs.junit.jupiter

    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'

    // This dependency is used by the application.
    implementation libs.guava

    // mariadb jconnector (single file no need change libs.versions.toml
    implementation 'org.mariadb.jdbc:mariadb-java-client:3.3.3'

    // using libs.versions.toml must editing this file 
    //implementation libs.mariadb.client

}
...

If you wish to useing Version Catalog Approach, use 2nd option for ./app/build.gradle and edit libs.version.toml

[versions]
guava = "32.1.3-jre"
junit-jupiter = "5.10.1"
mariadb = "3.3.3"

[libraries]
guava = { module = "com.google.guava:guava", version.ref = "guava" }
junit-jupiter = { module = "org.junit.jupiter:junit-jupiter", version.ref = "junit-jupiter" }
mariadb-client = { group = "org.mariadb.jdbc", name = "mariadb-java-client", version.ref = "mariadb" }


use Version Catalog Approach for complex project and involving multiple developers.

Edit ./app/src/main/java/com/dedetok/App.java

/*
 * This source file was generated by the Gradle 'init' task
 */
package com.dedetok;

import java.sql.*;

public class App {
    public String getGreeting() {
        return "Hello World!";
    }

    public static void main(String[] args) throws SQLException {
        System.out.println(new App().getGreeting());
        
        String dbUrl = "jdbc:mariadb://localhost:3306/mydatabase";
        String dbUName = "myuname";
        String dbPass = "mypass";
        
        Connection conn = DriverManager.getConnection(dbUrl, dbUName, dbPass);

    }
}

To generate single file jar for your project, edit  ./app/build.gradle

...
jar {
    duplicatesStrategy = DuplicatesStrategy.EXCLUDE

    // change with yours
    manifest {
        attributes "Main-Class": "com.dedetok.App"
    }

    from {
        configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) }
    }
}
...

You can run directly using java command

$ ./gradlew build
...
$ java -jar ./app/build/libs/app.jar
Hello World!

Your jar file location is ./app/build/libs/

Now you can edit  ./app/src/main/java/com/dedetok/App.java finish your project. Use any text editor if you wish.

Debian 13: bash to clean up unused gradle in folder $HOME/.gradle

stop any gradle daemon (better run this after you start your Debian)

copy paste this bash and change permission to execute

#!/bin/bash

# Set the cutoff date yyyy-mm-dd
CUTOFF_DATE="2025-08-01"

# Gradle folder
GRADLE_DIR="$HOME/.gradle"

# List of folders to clean
FOLDERS=("android" "build-scan-data" "caches" "daemon" "kotilin-profile" "native" "notifications" "undefined-build" "wrapper" ".tmp")

# 1. Stop Gradle Daemons first so files aren't locked
if [ -f "$GRADLE_DIR/daemon" ]; then
    echo "Stopping Gradle daemons..."
    gradle --stop 2>/dev/null || ./gradlew --stop 2>/dev/null
fi

echo "Cleaning Gradle folders in $GRADLE_DIR modified before $CUTOFF_DATE..."

for folder in "${FOLDERS[@]}"; do
    TARGET="$GRADLE_DIR/$folder"
    if [ -d "$TARGET" ]; then
        echo "Processing $TARGET..."
        # Find and delete files modified before the cutoff date
        find "$TARGET" -type f ! -newermt "$CUTOFF_DATE" -print -delete
        # Remove empty directories
        find "$TARGET" -type d -empty -print -delete
    else
        echo "Folder $TARGET does not exist, skipping."
    fi
done

echo "Cleanup complete."

Note:

• change CUTOFF_DATE for any desire date
• add or remove FOLDERS depends on your folder structure 

Android java: improving application screen form factor

In AndroidManifest.xml we can define screen form factor to used (androidmanifest.xml android:screenOrientation).

These are the options

1. "unspecified" : The default value. The system chooses the orientation. The policy it uses, and therefore the choices made in specific contexts, might differ from device to device.
2. "behind" : The same orientation as the activity that's immediately beneath it in the activity stack.
3. "landscape" : Landscape orientation (the display is wider than it is tall).
4. "portrait" : Portrait orientation (the display is taller than it is wide).
5. "reverseLandscape" : Landscape orientation in the opposite direction from normal landscape. Added in API level 9.
6. "reversePortrait" : Portrait orientation in the opposite direction from normal portrait. Added in API level 9.
7. "sensorLandscape" : Landscape orientation, but can be either normal or reverse landscape based on the device sensor. The sensor is used even if the user has locked sensor-based rotation. Added in API level 9.
8. "sensorPortrait" : Portrait orientation, but can be either normal or reverse portrait based on the device sensor. The sensor is used even if the user has locked sensor-based rotation. However, depending on the device configuration, upside-down rotation might not be allowed. Added in API level 9.
9. "userLandscape" : Landscape orientation, but can be either normal or reverse landscape based on the device sensor and the user's preference. Added in API level 18.
10. "userPortrait" : Portrait orientation, but can be either normal or reverse portrait based on the device sensor and the user's preference. However, depending on the device configuration, upside-down rotation might not be allowed. Added in API level 18.
11. "sensor" : The device orientation sensor determines the orientation. The orientation of the display depends on how the user is holding the device. It changes when the user rotates the device. Some devices, though, don't rotate to all four possible orientations, by default. To use all four orientations, use "fullSensor". The sensor is used even if the user locked sensor-based rotation.
12. "fullSensor" : The device orientation sensor determines the orientation for any of the four orientations. This is similar to "sensor", except this allows for any of the four possible screen orientations regardless of what the device normally supports. For example, some devices don't normally use reverse portrait or reverse landscape, but this enables those orientations. Added in API level 9.
13. "nosensor" : The orientation is determined without reference to a physical orientation sensor. The sensor is ignored, so the display doesn't rotate based on how the user moves the device.
14. "user" : The user's current preferred orientation.
15. "fullUser" : If the user has locked sensor-based rotation, this behaves the same as user, otherwise it behaves the same as fullSensor and allows any of the four possible screen orientations. Added in API level 18.
16. "locked" : Locks the orientation to its current rotation, whatever that is. Added in API level 18. 

Warning: To improve the layout of apps on form factors with smallest width >= 600dp, the system ignores the following values of this attribute for apps that target Android 16 (API level 36):

1.     portrait
2.     landscape
3.     reversePortrait
4.     reverseLandscape
5.     sensorPortrait
6.     sensorLandscape
7.     userPortrait
8.     userLandscape 

To create variant for table,  Goto main activity, on your main activity dropdown select "create table qualifier", it will create copy of main activity that require to modify to match tablet out. the layout is on layout -> main_activity -> main_activity.xml (sw600dp).

I use:

1. main_activity.xml
2. main_activity.xml (sw600dp)

main_activity.xml will be use for all mobile device, don't create main_activity (land). main_activity.xml (sw600dp) will be use on tablet. 

In case you want to lock phone to use portrait, delete main_activity.xml (land), you need to remove android:screenOrientation from AndroidManifest.xml. To make it consistent, this is sample of code in java for your main activity

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // 1. Enable edge-to-edge for Java Activities
        // You need to import androidx.activity.EdgeToEdge;
        EdgeToEdge.enable(this);
        super.onCreate(savedInstanceState);
        // Fragment
        // layout portrait or lanscape?
        // portrait my_fragment_container
        // langsacpe fragment_config_container, fragment_main_container
        setContentView(R.layout.activity_m); // general, let system choose between portrait and landscape
        // Check if landscape (two-pane) layout is active
        View config = findViewById(R.id.fragment_config_container);
        View main = findViewById(R.id.fragment_main_container);
        isTwoPane = (config != null && main != null); // already checked not null
        // Conditional Orientation Lock
        if (!isTwoPane) {
            // If single-pane (phone), force portrait before fragment transactions
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        }
        if (isTwoPane) {
            // dual-pane
            setFragment(R.id.fragment_config_container, new FragmentConfig());
            setFragment(R.id.fragment_main_container, new FragmentMain());
        } else {
            // single-pane
            // all phone must use this activity_m.xml (land)
            setFragment(R.id.my_fragment_container, new FragmentMain());
        }
        ...
    }

    private void setFragment(int containerId, Fragment fragment) {
        View container = findViewById(containerId);
        if (container == null) {
            //Log.e("dedetok", "Container ID " + containerId + " not found in this layout!");
            return;  // prevent crash
        }
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.replace(containerId, fragment);
        transaction.commit();

    } 

Immediately, lock screen for single pane (phone) to portrait, i.e. setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 

Android java: Releasing resource Activity/Fragment <-> AndroidViewModel <-> MyController

Activity/Fragment <-> AndroidViewModel <-> MyController

MyController will hold

1. Executor
2. MediaController 
3. Network access
4. Database access
5. Application context for above operation  

Proper way to clear the resource

1. Executor
           // MyAndroidViewModel onClear() has been reached
        if (myExecutor!=null) {
            myExecutor.shutdown();
            myExecutor = null;
        }
2. Media Controller
           if (myMediaController!=null) {
            myMediaController.releaseMediaSession(); // MUST BE CLEAR
            myMediaController = null;
        }
3. Network access
           myGetRadioLogo=null;
4. Database access  
           myDBAccess=null;
5. Application context
           appContext=null; // MUST SET NULL AT ONCLEAR

Fail to release these resources may lead to memory leak

Fail to release resource with not properly sequence may lead application crashed, this crash can be found on logcat.  

Android java: using DataLive for orientation change

I test it in Android 10 xiaomi mia2

What will happen when orientation change e.g. screen change or language change?

the object in activity will be destroyed. here is the sequence:

• after orientation change
  V  onPause
  V  onStop
  V  onDestrouy
• after flusing all data
  V  onCreate
  V  onCreate myClass :null
  V  MyClass constructor
  V  onCreateView myClass.getRandom
  V  onStart
  V  onResume 

At xiomi mia2, override public void onConfigurationChanged(Configuration newConfig) method did not called at all during screen orientation change, not appearred in logcat. except, you put android:configChanges in your layout.

Base on the android behave, these are the solution can be used to keep the object during configuration change:

1. Local persistence to handle process death for complex or large data. Persistent local storage includes databases or DataStore.
2. Retained objects such as ViewModel instances to handle UI-related state in memory while the user is actively using the app.
3. Saved instance state to handle system-initiated process death and keep transient state that depends on user input or navigation. 

ViewModel is recommended used for today an future, These are some options:

1. ViewModel    Holds UI data & logic    Core architecture component
2. ComputableLiveData (Deprecated)
3. MediatorLiveData    Combines multiple LiveData sources    Merging streams
4. MutableLiveData    Observable, mutable data    UI updates
5. SavingStateLiveData    LiveData with saved-state persistence    Restore after process death 

Comparison between AndroidViewModel vss ViewModel

AndroidViewModel	require Context for DB, prefs, etc.	gemini: Avoid if possible. Only use when you absolutely need Context. violates a core principle of good architecture: separation of concerns and testability.
ViewModel	UI logic without needing Context	Network requirement may use this, it does not need context

NOTE: Don’t store Activity or Fragment in VieModel nor AndroidViewModel! 

These are the java code for education, first text using direct access to object in activity, and second text using live data and AndroidViewModel. this code used AndroidViewModel, because I need application's context to access sqlite.

-- MyClass.java

package com.dedetok.testdataorientation;

import android.content.Context;
import android.util.Log;

import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;

import java.util.Random;

public class MyClass {
    // dummy
    Context context;

    boolean isCreated = false;
    int randomNumber=-1;

    public MyClass(Context context) {
        this.context = context;
        Log.v("deddetok", "MyClass constructor"); // debug

    }

    public String getRandom() {
        if (!isCreated) {
            Random random = new Random();
            randomNumber = random.nextInt(100);
            isCreated = true;
        }
        return String.valueOf(randomNumber);
    }

    public LiveData<String> getRandomLive() {
        if (!isCreated) {
            Random random = new Random();
            randomNumber = random.nextInt(100);
            isCreated = true;
        }
        MutableLiveData<String> returnValue = new MutableLiveData<>();
        returnValue.setValue(String.valueOf(randomNumber));

        return returnValue;
    }
}

-- MyAndroidViewModel

package com.dedetok.testdataorientation;

import android.app.Application;

import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;

public class MyAndroidViewModel extends AndroidViewModel {
    MyClass myClass;

    public MyAndroidViewModel(@NonNull Application application) {
        super(application);
        myClass = new MyClass(application);
    }

    public LiveData<String> getData() {
        return myClass.getRandomLive();
    }
}

-- MainActivity.java

package com.dedetok.testdataorientation;

import android.content.Context;
import android.content.res.Configuration;
import android.os.Bundle;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import androidx.activity.EdgeToEdge;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.AppCompatTextView;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.lifecycle.ViewModelProvider;

public class MainActivity extends AppCompatActivity {

    MyClass myClass = null;

    AppCompatTextView myTextView1, myTextView2;

    MyAndroidViewModel myAndroidViewModel;

    /* to preserve myclass
     * 1. Local persistence to handle process death for complex or large data. Persistent local storage includes databases or DataStore.
     * 2. Retained objects such as ViewModel instances to handle UI-related state in memory while the user is actively using the app.
     * 3. Saved instance state to handle system-initiated process death and keep transient state that depends on user input or navigation.
     */

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        Log.v("dedetok", "onCreate"); // debug


        myTextView1 = findViewById(R.id.textView1);
        myTextView2 = findViewById(R.id.textView2);

        Log.v("dedetok", "onCreate myClass :"+myClass); //
        // myTextView1
        if (myClass==null) {
            myClass = new MyClass(this);
        }
        myTextView1.setText(myClass.getRandom()); // work, created in memory

        // ✅ Get ViewModel (it survives rotation)
        // myTextView2
        myAndroidViewModel = new ViewModelProvider(this).get(MyAndroidViewModel.class);
        myAndroidViewModel.getData().observe(this, value -> {
            // 'value' is a plain String here
            myTextView2.setText(value);
        }); //

    }

    @Nullable
    @Override
    public View onCreateView(@Nullable View parent, @NonNull String name, @NonNull Context context, @NonNull AttributeSet attrs) {
        Log.v("dedetok", "onCreateView"); // debug
        //Log.v("dedetok", "onCreateView myClass.getRandom"); // debug
        //myTextView.setText(myClass.getRandom()); // crash textview not ready
        return super.onCreateView(parent, name, context, attrs);
    }

    /*
     * ## activity life cycle 2 ##
     */
    @Override
    protected void onStart() {
        super.onStart();
        Log.v("dedetok", "onCreateView myClass.getRandom"); // debug
        //myTextView1.setText(myClass.getRandom()); // work, view has been created
        myAndroidViewModel.getData().observe(this, value -> {
            // 'value' is a plain String here
            myTextView2.setText(value);
        }); // this is fine place

        Log.v("dedetok", "onStart"); // debug

    }

    /*
     * ## activity life cycle 3 ##
     */
    @Override
    protected void onResume() {
        super.onResume();

        Log.v("dedetok", "onResume"); // debug


    }

    /*
     * ## activity life cycle 4 ##
     */
    @Override
    protected void onPause() {
        Log.v("dedetok", "onPause"); // debug
        super.onPause();

    }

    /*
     * ## activity life cycle 5 ##
     */
    @Override
    protected void onStop() {
        Log.v("dedetok", "onStop"); // debug
        super.onStop();

    }

    /*
     * ## activity life cycle 6 ##
     */
    @Override
    protected void onDestroy() {
        Log.v("dedetok", "onDestrouy"); // debug

        super.onDestroy();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        Log.v("dedetok", "onConfigurationChanged"); // debug
    }
}

-- activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:minHeight="50dp"
        android:textSize="24sp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        />
    <androidx.appcompat.widget.AppCompatTextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView2"
        android:minHeight="50dp"
        android:textSize="24sp"
        app:layout_constraintTop_toBottomOf="@+id/textView1"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

Some of parts of this content generated by ChatGPT and Gemini with some modification.

Java Netbeans: using opencsv from url

Create a new Project Java with Maven project name e.g. TestOpenCSV

At Project Files, open pom.xml and add

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.dedetok</groupId>
    <artifactId>TestOpenCSV</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.release>17</maven.compiler.release>
        <exec.mainClass>com.dedetok.testopencsv.TestOpenCSV</exec.mainClass>
    </properties>
    <dependencies>
    <dependency>
        <groupId>com.opencsv</groupId>
        <artifactId>opencsv</artifactId>
        <version>5.9</version> <!-- or latest -->
    </dependency>
</dependencies>
</project>

You can use beans to map the result, or manually process the csv files. for data size bigger then 1 millions, there is deference about 1 second, it is better to manually process. Here are code to test, before you use it in production. Feel free to change any the code to meet your requirement.

Classs Radio

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package com.dedetok.testopencsv;

import com.opencsv.bean.CsvBindByName;

/**
 *
 * @author dedetok
 */
public class Radio {
    @CsvBindByName(column = "country")
    private String country;

    @CsvBindByName(column = "city")
    private String city;

    @CsvBindByName(column = "radioname")
    private String radioname;

    @CsvBindByName(column = "url_logo")
    private String url_logo;

    @CsvBindByName(column = "url_stream")
    private String url_stream;

    public String getCountry() { return country; }
    public String getCity() { return city; }
    public String getRadioname() { return radioname; }
    public String getUrl_logo() { return url_logo; }
    public String getUrl_stream() { return url_stream; }
}

Main class

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 */

package com.dedetok.testopencsv;

import com.opencsv.CSVParser;
import com.opencsv.CSVParserBuilder;
import com.opencsv.CSVReader;
import com.opencsv.CSVReaderBuilder;
import com.opencsv.exceptions.CsvValidationException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.opencsv.bean.CsvBindByName;
import com.opencsv.bean.CsvToBean;
import com.opencsv.bean.CsvToBeanBuilder;
import java.util.List;

/**
 *
 * @author dedetok
 */
public class TestOpenCSV {

    static String urlString = "https://raw.githubusercontent.com/dedetok/myradiolist/refs/heads/main/myradio_radiolist.csv";
    
    public static void main(String[] args) throws CsvValidationException {
        System.out.println("Hello World!");
        
        // start function

        try {
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            // Check response
            int status = connection.getResponseCode();
            if (status == 200) {
                // Configure parser: semicolon separator, double-quote as quote char
                InputStreamReader reader = new InputStreamReader(connection.getInputStream());
                // Start For parsing manual
                CSVParser parser = new CSVParserBuilder()
                        .withSeparator(';')
                        .withQuoteChar('"')
                        .build();
                //CSVReader csvReader = new CSVReader(reader);
                CSVReader csvReader = new CSVReaderBuilder(reader)
                        .withCSVParser(parser)
                        //.withSkipLines(1) // skip header if needed
                        .build();
                String[] nextLine;
                int i=1;
                while ((nextLine = csvReader.readNext()) != null) {
                    for (String cell : nextLine) {
                        System.out.print(cell + " | ");
                    }
                    i++;
                    System.out.println();
                    if (i==5) {
                        break;
                    }
                }
                // End For parsing manual
                // start convert directly to list<Radio> using opencsv beans
                /*
                CsvToBean<Radio> csvToBean = new CsvToBeanBuilder<Radio>(reader)
                    .withType(Radio.class)
                    .withSeparator(';')
                    .withQuoteChar('"')
                    .withIgnoreLeadingWhiteSpace(true)
                    .build();
                List<Radio> radios = csvToBean.parse();
                System.out.println("Loaded " + radios.size() + " radios!");
                
                // debug
                for (int i = 0; i < Math.min(5, radios.size()); i++) {
                    Radio r = radios.get(i);
                    System.out.println(
                        r.getCountry() + " | " +
                        r.getCity() + " | " +
                        r.getRadioname() + " | " +
                        r.getUrl_logo() + " | " +
                        r.getUrl_stream()
                    );
                }
                */
                // end convert directly to list<Radio> using opencsv beans

            }
        } catch (MalformedURLException ex) {
            Logger.getLogger(TestOpenCSV.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(TestOpenCSV.class.getName()).log(Level.SEVERE, null, ex);
        }      
    }
}

 Code is write with collaboration with chatgpt 

 

Android Studio 2024.1.4: backup and how you migrate your old project

Android Studio move so fast, the developer and ide tools are racing each other.

These are must you backup: 

1. Project name
2. Your key file i.e jks for your project
3. your project source
1. <root_app> remove folders .gradle .idea and build, remove file .gitignore
2. <root_app>/app remove folders build, libs and release, remove file .gitignore
3. <root_app>/gradle remove file ./gradle/wrapper/gradle-wrapper.jar

For upgrading from old project, and your project does not have libs.versions.toml file:

1. Create it (see below) or copy from other project <root_app>/gradle/libs.versions.toml.
2. change build.gradle.kts (:app)
   
   plugins {
    id("com.android.application")
}
   
   into 
   
   plugins {
    alias(libs.plugins.android.application)
}
   
   Change dependency 
   
   dependencies {

    implementation("androidx.appcompat:appcompat:1.7.1")
    implementation("com.google.android.material:material:1.12.0")
    implementation("androidx.constraintlayout:constraintlayout:2.2.1")
    testImplementation("junit:junit:4.13.2")
    androidTestImplementation("androidx.test.ext:junit:1.2.1")
    androidTestImplementation("androidx.test.espresso:espresso-core:3.6.1")
    implementation("com.google.android.gms:play-services-ads-lite:24.0.0")

}
   
   into
   
   dependencies {

    implementation(libs.appcompat)
    implementation(libs.material)
    testImplementation(libs.junit)
    androidTestImplementation(libs.ext.junit)
    androidTestImplementation(libs.espresso.core)

    // admob
    implementation(libs.play.services.ads)
}
3. Update your libs.versions.toml, revise the version if necessary:
   
   [versions]
agp = "8.13.0"
junit = "4.13.2"
junitVersion = "1.3.0"
espressoCore = "3.7.0"
appcompat = "1.7.1"
material = "1.13.0"
playServicesAds = "24.7.0"

[libraries]
junit = { group = "junit", name = "junit", version.ref = "junit" }
ext-junit = { group = "androidx.test.ext", name = "junit", version.ref = "junitVersion" }
espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
appcompat = { group = "androidx.appcompat", name = "appcompat", version.ref = "appcompat" }
material = { group = "com.google.android.material", name = "material", version.ref = "material" }
play-services-ads = { module = "com.google.android.gms:play-services-ads", version.ref = "playServicesAds" }

[plugins]
android-application = { id = "com.android.application", version.ref = "agp" }

Note: if you have other external dependency, keep the library first, and migrate after common library successfully upgraded.

To create libs.versions.toml, at left side Project Files -> gradle -> New -> File, name it with: libs.versions.toml. Continue step 2 above.

This is example of external library, how to move jsoup into libs.versions.toml

Change build.gradle.kts (:app) from  

dependencies {
    ...
    implementation("org.jsoup:jsoup:1.21.2") // jsoup

}

change into

dependencies {
    ....
    implementation(libs.jsoup)
}

And add into libs.versions.toml

[versions]
...
# Define the version number
jsoup = "1.21.2"
...
[libraries]
...
# Define the library coordinates, referencing the version above
jsoup = { group = "org.jsoup", name = "jsoup", version.ref = "jsoup" }
...

 

Netbeans: using maven to connect to mariadb

1. Create project "Java with Maven" -> "Java Application"
2. Under tab "Project" -> Project Files, edit pom.xml and add mariadb jconnect client
   <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
...
  <dependencies>
...
  <dependency>
    <groupId>org.mariadb.jdbc</groupId>
    <artifactId>mariadb-java-client</artifactId>
    <version>3.5.3</version>
    </dependency>
  </dependencies>
...
</project>
3. Test connection using this code
     public static void main(String[] args) throws SQLException, ClassNotFoundException {
    // TODO Auto-generated method stub
    String muser = "my_user";
    String mpass = "my_password";
    String murl = "jdbc:mariadb://localhost:3306/my_database_name";
    Class.forName("org.mariadb.jdbc.Driver");
    Connection connection = DriverManager.getConnection(murl, muser, mpass);
    System.out.println("ok");
  }

Netbeans: Netbeans 25 with JDK 17 add MariaDB Connector/J 3.5 into Java Project Maven

Netbeans 25 can be download from https://www.apache.org/dyn/closer.lua/netbeans/netbeans/25/netbeans-25-bin.zip. Extract it, it will create folder netbeans. 

On debian, to run netbeans:

[home_user]\netbeans/bin/netbeans

On window, to run netbeans (windows 64):

[folder]\netbeans\bin\netbeans64.exe

Note: on windows, if you want to clean install remove/delete folder C:\Users\[username]\AppData\Roaming\NetBeans\[any_previous].

Download mariadb-java-client-3.5.3.jar from https://mariadb.com/downloads/connectors/connectors-data-access/java8-connector/ and choose mariadb-java-client-3.5.3.jar.

Add mariadb-java-client-3.5.3.jar into project

1. create a New Project -> Java with maven -> Java application
2. in tab Files under your project, create folder libjar
3. copy mariadb-java-client-3.5.3.jar
4. in Project -> your project, right click on Dependencies, Add Dependency:
   Group ID: org.mariadb.jdbc
Artifact ID: mariadb-java-client
Version: 3.5.3
5. Scope: Runtime
   
6. done. 

Run your database and test your project by editing your java files:

    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        // TODO Auto-generated method stub
        String muser = "my_user";
        String mpass = "my_password";
        String murl = "jdbc:mariadb://localhost:3306/my_database_name";
        Class.forName("org.mariadb.jdbc.Driver");
        Connection connection = DriverManager.getConnection(murl, muser, mpass);
        System.out.println("ok");
    }

Add mariadb to Services:

1. to add mariadb connector j, go to Services -> Right Click Databases -> New Connection.
2. Select MariaDB (MySQL-compatible).
3. select jar file.
4. next.
5. fill/adjust username, password and database name.
6. test connection.
7. if successfull, next.
8. leave default connection info and finish.

You can manage your mariadb database from Service.

Eclipse 2025-03 (4.35.0) with JDK 17 add MariaDB Connector/J 3.5 into Project

Download mariadb-java-client-3.5.3.jar from https://mariadb.com/downloads/connectors/connectors-data-access/java8-connector/ 

Open eclipse:

1. create folder lib
2. copy mariadb-java-client-3.5.3.jar into [workspace_root]/myca/lib/
3. open project properties -> Build Path -> Configure Build Path
4. go to tab Libraries and click Classpath -> Add External JARS, i.e. [Workspace_root]/myca/lib/mariadb-java-client-3.5.3.jar 
5. apply and close

To test mariadb-client without without Eclipse, write TesCon.java using any editor:

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

public class TesCon {

    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        // TODO Auto-generated method stub
        String muser = "my_user";
        String mpass = "my_password";
        String murl = "jdbc:mariadb://localhost:3306/my_database_name";
        Class.forName("org.mariadb.jdbc.Driver");
        Connection connection = DriverManager.getConnection(murl, muser, mpass);
        System.out.println("ok");
    }

}

Run from command line/terminal

$> javac TesCon.java

$> java -cp ./:./mariadb-java-client-3.5.3.jar TesCon


window:

D:\>javac TesCon.java

D:\>java -cp .\;.\mariadb-java-client-3.5.3.jar TesCon

In Eclipse:

1. create a new Java Project
2. optional: create package
3. add a Class with Name TesCon.java
4. copy paste the code above. If you create a package, replace all after "package [your_package];"
5. run project

Every major release eclipse, adding external jar, especially j connector, into eclipse is very painful. Loading mariadb connector j using eclipse is Fail.

Replace old Eclipse to 2025-3 (clean install windows/Debian)

Assume: you used Eclipse eclipse in tar.gz or zip, not using installer.

In Windows delete this directory

1. c:\Users\[username]/.eclipse
2. [home]\eclipse -> your old eclipse
3. [workspace]\.metadata -> your existing workspace for eclipse
   

In Debian delete this directory

1. [home_user]/.eclipse
2. [home_user]/eclipse -> your old eclipse
3. [home_user]/[workspace]/.metadata -> your existing workspace for eclipse

Extract eclipse-java-2025-03-R-linux-gtk-x86_64.tar.gz and put "eclipse" folder into [home].

Run your eclipse, select your existing workspace and install all software you need e.q. WindowBuilder.

Note: Windows will ask your permission to prevent Defender scan your Eclipse for performance. I recommended to exclude Eclipse.

To open existing project in your existing workspace

1. Import -> General -> Existing Project into Workspace -> Next
2. Point "Select root directory" to your existing project directory.
3. Finish

 

android java: google admob policy collected data checklist

 

In May 2021, Google Play announced the new Data safety section https://developers.google.com/admob/android/privacy/play-data-disclosure. All application must declare data safety, include if application has 3rd partly like Google Google Mobile Ads.

Unfortunately, the guidance data disclosure in https://developers.google.com/admob/android/privacy/play-data-disclosure does not clear. It does mention clues what Google Mobile Ads SDK do with our client data. Here are the clues:

Data	By default, the Google Mobile Ads SDK...
IP address	Collects device's IP address, which may be used to estimate the general location of a device.
User product interactions	Collects user product interactions and interaction information, including app launch, taps, and video views.
Diagnostic information	Collects information related to the performance of your app and the SDK, including crash logs, app launch time, hang rate, and energy usage.
Device and Account identifiers	Collects Android advertising (ad) ID, app set ID, and, if applicable, other identifiers related to signed-in accounts on the device.

We must fill in Data safety section:

A.    Overview
Information about what to fill.

B.    Data Collection and Security

1.     Does your app collect or share any of the required user data types? Y

·       Is all of the user data collected by your app encrypted in transit? Y

·       þ My app does not allow users to create an account

•       Can users login to your app with accounts created outside of the app? N

·       Do you provide a way for users to request that their data is deleted? (Optional) N

C.    Data Types

1.     Location:

·       Approximate location

2.     Personal info:

·       User IDs

·       Other info

3.     App activity:

·       App interactions

·       In-app search history

·       Installed apps

4.     App info and performance:

·       Crash logs

·       Diagnostics

·       Other app performance data

5.     Device or other IDs

·       Device or other IDs

D.    Data usage and handling

1.     Personal info - User IDs & Other info

·       Is this data collected, shared, or both?
þ Collected & Shared

·       Is this data processed ephemerally?
þ No, this collected data is not processed ephemerally

·       Is this data required for your app, or can users choose whether it's collected?
þ Data collection is required (users can't turn off this data collection)

·       Why is this user data collected? Select all that apply.
þ Advertising or marketing

·       Why is this user data shared? Select all that apply.
þ Advertising or marketing

2.     Location - Approximate location:

·       Is this data collected, shared, or both?
þ Collected & Shared

·       Is this data processed ephemerally?
þ No, this collected data is not processed ephemerally

·       Is this data required for your app, or can users choose whether it's collected?
þ Data collection is required (users can't turn off this data collection)

·       Why is this user data collected? Select all that apply.
þ Advertising or marketing

·       Why is this user data shared? Select all that apply.
þ Advertising or marketing

3.     App info and performance - Crash logs; Diagnostics; & Other app performance data

·       Is this data collected, shared, or both?
þ Collected & Shared

·       Is this data processed ephemerally?
þ No, this collected data is not processed ephemerally

·       Is this data required for your app, or can users choose whether it's collected?
þ Data collection is required (users can't turn off this data collection)

·       Why is this user data collected? Select all that apply.
þ Analytics

·       Why is this user data shared? Select all that apply.
þ Analytics

4.     App activity - App interactions; In-app search history; & Installed apps

·       Is this data collected, shared, or both?
þ Collected & Shared

·       Is this data processed ephemerally?
þ No, this collected data is not processed ephemerally

·       Is this data required for your app, or can users choose whether it's collected?
þ Data collection is required (users can't turn off this data collection)

·       Why is this user data collected? Select all that apply.
þ Advertising or marketing

·       Why is this user data shared? Select all that apply.
þ Advertising or marketing

5.     Device or other IDs - Device or other IDs:

·       Is this data collected, shared, or both?
þ Collected & Shared

·       Is this data processed ephemerally?
þ No, this collected data is not processed ephemerally

·       Is this data required for your app, or can users choose whether it's collected?
þ Data collection is required (users can't turn off this data collection)

·       Why is this user data collected? Select all that apply.
þ Advertising or marketing

·       Why is this user data shared? Select all that apply.
þ Advertising or marketing