Error:Execution failed for task ':app:transformClassesWithDexForDebug'

Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_65.jdk/Contents/Home/bin/java'' finished with non-zero exit value 2

  检查项目中各个类库的jar包 有重复的包！