protected final String twoColumns(String s1, String s2) {
    int w1 = getWidth1();
    int w2 = getWidth2();

    try {
      if (w1 == 0) {
        int len2 = s2.length();
        StringWriter sw = new StringWriter(len2 * 2);
        IndentingWriter iw = new IndentingWriter(sw, w2, separator);

        iw.write(s2);
        if ((len2 == 0) || (s2.charAt(len2 - 1) != '\n')) {
          iw.write('\n');
        }
        iw.flush();

        return sw.toString();
      } else {
        return TwoColumnOutput.toString(s1, w1, separator, s2, w2);
      }
    } catch (IOException ex) {
      throw new RuntimeException(ex);
    }
  }
Combines a pair of strings as two columns, or if this is one-column output, format the
otherwise-second column.

@param s1 {@code non-null;} the first column's string
@param s2 {@code non-null;} the second column's string
@return {@code non-null;} the combined output
android/android_framework/dex-maker/src/main/java/com/android/dx/command/dump/BaseDumper.java