package prophecy.common;

public class JSONMinify {
  public static String minify(String jsonString) {
    boolean in_string = false;
    boolean in_multiline_comment = false;
    boolean in_singleline_comment = false;
    char string_opener = 'x'; // unused value, just something that makes compiler happy

    StringBuilder out = new StringBuilder();
    for (int i = 0; i < jsonString.length(); i++) {
      // get next (c) and next-next character (cc)

      char c = jsonString.charAt(i);
      String cc = jsonString.substring(i, Math.min(i+2, jsonString.length()));

      // big switch is by what mode we're in (in_string etc.)
      if (in_string) {
        if (c == string_opener) {
          in_string = false;
          out.append(c);
        } else if (c == '\\') { // no special treatment needed for \\u, it just works like this too
          out.append(cc);
          ++i;
        } else
          out.append(c);
      } else if (in_singleline_comment) {
        if (c == '\r' || c == '\n')
          in_singleline_comment = false;
      } else if (in_multiline_comment) {
        if (cc.equals("*/")) {
          in_multiline_comment = false;
          ++i;
        }
      } else {
        // we're outside of the special modes, so look for mode openers (comment start, string start)
        if (cc.equals("/*")) {
          in_multiline_comment = true;
          ++i;
        } else if (cc.equals("//")) {
          in_singleline_comment = true;
          ++i;
        } else if (c == '"' || c == '\'') {
          in_string = true;
          string_opener = c;
          out.append(c);
        } else if (!Character.isWhitespace(c))
          out.append(c);
      }
    }
    return out.toString();
  }
}

From http://jsonminify.tinybrain.de with greetings.