Execution failed for task: ClassWithDexForDebug

Hey everyone. I am new to android app development, and I am trying to run my app on the emulator. However, on the console, there is 1 error and it states exactly this:

"
Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command 'C:\Program Files\Java\jdk1.7.0_79\bin\java.exe'' finished with non-zero exit value 1
"

When I run the AVD emulator to test my app, I can't see my app anywhere on the screen. I believe it is because of this error that occurs when the emulator is loading up. Can anyone help me please?