Fixing Gradle “Duplicate files copied”

I just tried to develop android apps with android studio. After I added new dependency then rebuild my project I got an error “Duplicate files copied”.
Here is the stacktrace of my gradle build:

Error:Execution failed for task ':app:packageDebug'.
> Duplicate files copied in APK META-INF/LICENSE.txt
	File 1: C:\Users\Administrator\.gradle\caches\modules-2\files-2.1\joda-time\joda-time\2.8.2\d27c24204c5e507b16fec01006b3d0f1ec42aed4\joda-time-2.8.2.jar
	File 2: C:\Users\Administrator\.gradle\caches\modules-2\files-2.1\org.twitter4j\twitter4j-core\4.0.1\37fd1d1eb3ed57916c9fdd1ea1f6c3afce778c7c\twitter4j-core-4.0.1.jar

I solved the problem just add a few code below in my app “build.gradle”

packagingOptions {
   exclude 'META-INF/LICENSE.txt'

And here is my full app “build.gradle” config:

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId ""
        minSdkVersion 14
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), ''
    packagingOptions {
        exclude 'META-INF/LICENSE.txt'