title: Multiple "Duplicate Class" Errors in Android Studio
body: <p>So I'm trying to run my Android App but I get following Errors:</p>
  
  <pre><code>Duplicate class org.jetbrains.annotations.Contract found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.Nls found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.NonNls found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.NotNull found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.Nullable found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.PropertyKey found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  Duplicate class org.jetbrains.annotations.TestOnly found in modules annotations-13.0.jar (org.jetbrains:annotations:13.0) and jetified-kotlin-compiler-embeddable-1.3.21.jar (org.jetbrains.kotlin:kotlin-compiler-embeddable:1.3.21)
  
  Go to the documentation to learn how to Fix dependency resolution errors.
  
  </code></pre>
  
  <p>I can't really wrap my head around these kinds of errors since I'm not even using Kotlin in any way in my entire app. It's configured as a Java app.</p>
  
  <p>My build.gradle (Module: App) looks like this:</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 29
      buildToolsVersion "29.0.2"
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
      defaultConfig {
          applicationId "com.example.app"
          minSdkVersion 15
          targetSdkVersion 29
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
          multiDexEnabled true
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
          }
      }
      packagingOptions {
          exclude "**/kotlin/**"
      }
  }
  
  dependencies {
      implementation fileTree(dir: 'libs', include: ['*.jar'])
      implementation 'androidx.appcompat:appcompat:1.0.2'
      implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
      testImplementation 'junit:junit:4.12'
      androidTestImplementation 'androidx.test.ext:junit:1.1.0'
      androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
      implementation 'com.journeyapps:zxing-android-embedded:2.0.1@aar'
      implementation 'com.journeyapps:zxing-android-integration:2.0.1@aar'
      implementation 'com.google.zxing:core:3.2.1'
      implementation 'me.dm7.barcodescanner:zxing:1.9'
      // https://mvnrepository.com/artifact/org.web3j/parity
      implementation 'org.web3j:core:4.5.7'
      implementation 'org.web3j:parity:4.5.5'
  }
  </code></pre>
  
  <p>The other build.gradle (Project: App) looks like this:</p>
  
  <pre><code>// Top-level build file where you can add configuration options common to all sub-projects/modules.
  
  buildscript {
      repositories {
          mavenCentral()
          google()
          jcenter()
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.5.1'
  
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
      }
  }
  
  allprojects {
      repositories {
          mavenCentral()
          google()
          jcenter()
  
      }
  }
  
  task clean(type: Delete) {
      delete rootProject.buildDir
  }
  </code></pre>
  
  <p>I added <code>mavenCentral()</code> and <code>jcenter()</code> to the repositories after I read other questions/answers on StackOverflow from people with similar Duplicate Class Errors.</p>