public void dumpOriginalLineNumbers(int[] lineMapping) {
    if (lineMapping.length > 0) {
      myLineMapping = new HashMap<>();
      for (int i = 0; i < lineMapping.length; i += 2) {
        int key = lineMapping[i + 1];
        Set<Integer> existing = myLineMapping.computeIfAbsent(key, k -> new TreeSet<>());
        existing.add(lineMapping[i]);
      }
    }
  }
Recursive reformatting of groups.
If the group's content would take you over the specified preferred line length, then the group is applied.

- This algorithm usually ensures that if a group is applied, then all the group's parents in the tree are also
  applied. This tends to produce a nice structured output with well-placed potential newlines.
- The formatter keeps track of the offset as a result of the reformat at each character in the text buffer, and
  applies them to the bytecode offsets afterwards, so that the line number mappings don't get messed up.
src/org/jetbrains/java/decompiler/util/TextBuffer.java