gcm end points for push notification to android device giving strange error

[NavinRaj Pandey via StackOverflow]

follwing this github project and instruction

here

I am trying to implement push notification to android device from google back end. the backend part runs successfully in localhost but when I try to run the android project I get a strange error in build process every time.

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 'C:\Program Files\Java\jdk1.8.0_60\bin\java.exe'' finished with non-zero exit value 2**

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