private static void printUsage() {
    System.out.println("Usage: DexMerger <out.dex> <a.dex> <b.dex> ...");
    System.out.println();
    System.out.println(
        "If a class is defined in several dex, the class found in the first dex will be used.");
  }
minimum number of wasted bytes before it's worthwhile to compact the result
android/android_framework/dex-maker/src/main/java/com/android/dx/merge/DexMerger.java