Error:Execution failed for task ':Blok:dexDebug'.
> com.android.ide.common.internal.LoggedErrorException: Failed to run command:
    /home/backman/android/sdk/build-tools/android-4.4.2/dx --dex --output /home/backman/AndroidStudioProjects/Blok/Blok/build/dex/debug /home/backman/AndroidStudioProjects/Blok/Blok/build/classes/debug /home/backman/AndroidStudioProjects/Blok/Blok/build/dependency-cache/debug /home/backman/AndroidStudioProjects/Blok/Blok/build/pre-dexed/debug/core-bcdbe5f84dd399255abb34d14ce9def109db2534.jar
  Error Code:
    2
  Output:
    UNEXPECTED TOP-LEVEL EXCEPTION:
    com.android.dex.DexException: Multiple dex files define Lcom/google/zxing/BarcodeFormat;
        at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:594)
        at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:552)
        at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:533)
        at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:170)
        at com.android.dx.merge.DexMerger.merge(DexMerger.java:188)
        at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:439)
        at com.android.dx.command.dexer.Main.runMonoDex(Main.java:287)
        at com.android.dx.command.dexer.Main.run(Main.java:230)
        at com.android.dx.command.dexer.Main.main(Main.java:199)
        at com.android.dx.command.Main.main(Main.java:103)