Automatically ellipsize a string in Java

Question

Is there a method in Java to automatically ellipsize a string? Just in Java, not other libraries.

Thanks.

Answer 1

Depending on your use case, it might be useful to put the ellipsis between letters (i.e. add letters at the end to provide some context):

/**
 * Puts ellipses in input strings that are longer than than maxCharacters. Shorter strings or
 * null is returned unchanged.
 * @param input the input string that may be subjected to shortening
 * @param maxCharacters the maximum characters that are acceptable for the unshortended string. Must be at least 3, otherwise a string with ellipses is too long already.
 * @param charactersAfterEllipsis the number of characters that should appear after the ellipsis (0 or larger) 
 * @return the truncated string with trailing ellipses
 */
public static String ellipsize(String input, int maxCharacters, int charactersAfterEllipsis) {
  if(maxCharacters < 3) {
    throw new IllegalArgumentException("maxCharacters must be at least 3 because the ellipsis already take up 3 characters");
  }
  if(maxCharacters - 3 > charactersAfterEllipsis) {
    throw new IllegalArgumentException("charactersAfterEllipsis must be less than maxCharacters");
  }
  if (input == null || input.length() < maxCharacters) {
    return input;
  }
  return input.substring(0, maxCharacters - 3 - charactersAfterEllipsis) + "..." + input.substring(input.length() - charactersAfterEllipsis);
}

There are also more sophisticated features you might want from you ellipsis algorithm: If you need to place the text into a graphical element and you are using a proportional font, then you must measure the length of the String.

For Swing/AWT that would be java.awt.Font.getStringBounds. In such a case, a simple algrithm would cut the string one letter at a time and add the ellipsis, until the string fits into the limit given. If used often, the bisection method elaborated in http://www.codeproject.com/KB/cs/AutoEllipsis.aspx?msg=3278640 (C#, but should be easy enough to translate to Java) may save some processor cycles.

Answer 2

This method will return the ellipsized String:

String ellipsize(String input, int maxLength) {
    String ellip = "...";
    if (input == null || input.length() <= maxLength 
           || input.length() < ellip.length()) {
        return input;
    }
    return input.substring(0, maxLength - ellip.length()).concat(ellip);
}

Answer 3

There is not. But here's another crack at a simple method to do this.

String ellipsize(String input, int maxLength) {
  if (input == null || input.length() < maxLength) {
    return input;
  }
  return input.substring(0, maxLength) + "...";
}

Answer 4

A oneliner which of course does not outperform the other offered solutions:

longString.replaceFirst("(.{5}).+(.{5})", "$1...$2")

Will leave only first and last 5 characters and put ... in the middle.

Answer 5

Sure, try this one:

public static String ellipsise (String input, int maxLen) {
    if (input == null)
        return null;
    if ((input.length() < maxLen) || (maxLen < 3))
        return input;
    return input.substring (0, maxLen - 3) + "...";
}

This has the advantage of fixing the bug where the King's English is not used properly :-)