void compact() {
    for (int i = 0; i < catchLabels.size(); i++) {
      while (catchLabels.get(i).isEmpty()) {
        catchLabels.set(i, catchLabels.get(i).primarySuccessor);
      }
    }
    while (primarySuccessor != null && primarySuccessor.isEmpty()) {
      primarySuccessor = primarySuccessor.primarySuccessor;
    }
    while (alternateSuccessor != null && alternateSuccessor.isEmpty()) {
      alternateSuccessor = alternateSuccessor.primarySuccessor;
    }
  }
contains the instruction to jump to if the if is true
android/android_framework/dex-maker/src/main/java/com/android/dx/Label.java