在Java中自动省略字符串

Question

Java中有没有自动省略字符串的方法？只是在Java中，而不是在其他库中

谢谢

Answer 1

根据您的用例，在字母之间加省略号可能会很有用（即在末尾加字母以提供一些上下文）：

/**
 * 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);
}

您可能还希望从省略号算法中获得更复杂的功能：如果需要将文本放置到图形元素中，并且使用比例字体，则必须测量字符串的长度

对于Swing/AWT，这将是java.awt.Font.getStringBounds。在这种情况下，一个简单的算法会将字符串一次剪切一个字母，并添加省略号，直到字符串符合给定的限制。如果经常使用，在http://www.codeproject.com/KB/cs/AutoEllipsis.aspx?msg=3278640（C#，但应该很容易翻译成Java）中详述的二分法可能会节省一些处理器周期

Answer 2

oneliner当然不会比其他提供的解决方案表现更好：

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

将只留下第一个和最后5个字符，并将。。。在中间。

Answer 3

此方法将返回省略的字符串：

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);
}