What does "Program type already present" mean?

I'm trying to build an app in Android Studio. After adding the Eclipse Paho library as a gradle dependency(or is it Maven? I'm new to the Android ecosystem), I got the following error:

Program type already present: android.support.v4.accessibilityservice.AccessibilityServiceInfoCompat
Message{kind=ERROR, text=Program type already present: android.support.v4.accessibilityservice.AccessibilityServiceInfoCompat, sources=[Unknown source file], tool name=Optional.of(D8)}

I've checked many different StackOverflow questions relating to this error, but the answers are all specific to certain libraries. I'm looking not only for a solution to the error, but an understanding of what the error means. That way it'll be easier for people to figure out solutions for their specific cases. So far, no answer has provided that.

From other StackOverflow answers, I've gathered that it has something to do with my gradle file. So, here's app/build.gradle:

apply plugin: 'com.android.application'
android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "---REDACTED FOR PRIVACY---"
        minSdkVersion 15
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}
dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:27.1.0'
    implementation 'com.android.support:support-media-compat:27.1.0'
    implementation 'com.android.support:support-v13:27.1.0'
    implementation 'com.google.android.gms:play-services-maps:12.0.1'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'org.eclipse.paho:org.eclipse.paho.client.mqttv3:1.0.2'
    implementation 'org.eclipse.paho:org.eclipse.paho.android.service:1.0.2'
}

repositories {
    maven { url 'https://repo.eclipse.org/content/repositories/paho-releases/' }
} 

For me just cleaning the project solved the issue

Using Terminal :

./gradlew clean

Using Android Studio :

Build (menu) > Clean Project

This problem usually come from a naming conflict, in your case the support-v4 library, which is use by several libraries.

To find the list of dependencies for the module app (default module's name for the app) we can do a gradlew app:dependencies to retrieve a list of all the libraries.

We found that support-v4 is used by:

//short version of the dependencies list highlighting support-v4
+--- com.android.support:support-v13:27.1.0
|    \--- com.android.support:support-v4:27.1.0

+--- com.google.android.gms:play-services-maps:12.0.1
|    +--- com.google.android.gms:play-services-base:12.0.1
|    |    +--- com.google.android.gms:play-services-basement:12.0.1
|    |    |    +--- com.android.support:support-v4:26.1.0 -> 27.1.0 (*)

+--- org.eclipse.paho:org.eclipse.paho.android.service:1.0.2
|    +--- com.google.android:support-v4:r7  // <- problem here

We see that the support-v4 on Maps will use the version provided from support-v13.

We also see that the eclipse library is using another version (r7 ??).

To resolve your issue, you can try to exclude the module support-v4 from this eclipse library like this:

implementation ('org.eclipse.paho:org.eclipse.paho.android.service:1.0.2') {
    exclude module: 'support-v4'
}

Then you should be able to compile your application.

Btw you should take care that the eclipse module won't break by testing your code.

From official Doc

If a class appears more than once on the runtime classpath, you get an error similar to the following:

Program type already present com.example.MyClass

This error typically occurs due to one of the following circumstances:

• A binary dependency includes a library that your app also includes as a direct dependency.

  For example, your app declares a direct dependency on Library A and Library B, but Library A already includes Library B in its binary. To resolve this issue, remove Library B as a direct dependency.

• Your app has a local binary dependency and a remote binary dependency on the same library.

To resolve this issue, remove one of the binary dependencies. ( See if same library is added as jar and gradle dependency)

It's happened to me also but in my case, I try to include different dependencies that have same class using debugApi & Api so Android Studio marked as duplicate class, so I solved the issue by using debugApi & releaseApi to include different dependencies based on the build variant.

In my case it mean I have 2 *.jar file or 2 libary some where in source code. For example: I have 2 youtube.jar in app/libary and module/libary Delete the redundant once and it will be fine

Add Support library to app level Gradle file >implementation 'com.android.support:design:27.1.0'

I hope it helps somebody, a Build > Clean Project worked for me.

Problem for this issue - If you use the library as module & same library as dependency in another library.

Example: LibraryA imported as Module & same LibraryA added as dependency in any other library module.

How to fix this issue?

Solution 1 - > if you want to keep both -> Just refactor the package name of LibraryA module

Solution 2 - > remove the LibraryA dependency and use the module

> implementation project(':LibraryA')

The reason I was getting this error was because I converted a Java file to a Kotlin one like this:

Code (menu) -> Convert Java file to Kotlin file

The old Java class must have still been hanging around on the classpath resulting in a duplicate. Doing a clean fixed it:

Build (menu) -> Clean Project

I have the same problem but with my project's internal library after updating from Android Studio 4.0.2 to 4.1. I have searched and tried many things without success. If you guys have the same case as me, I hope this answer can help. What I have done:

1. Clean Project then Rebuild Project - failed
2. Invalidate Caches / Restart - failed
3. Delete global Gradle caches (/User/username/.gradle/caches for macOS) - failed
4. Investigating app dependencies via terminal with the command: ./gradlew app:dependencies or via Gradle tool window: project->Tasks->android->androidDependencies - nothing suspicious
5. Delete .gradle and .idea from my root project - success (although I'm not sure if I need to delete both. Maybe just delete one of them also working)