线边界

原文： https://docs.oracle.com/javase/tutorial/i18n/text/line.html

格式化文本或执行换行的应用程序必须找到潜在的换行符。您可以使用getLineInstance方法创建的BreakIterator找到这些换行符或边界：

  1. BreakIterator lineIterator =
  2.     BreakIterator.getLineInstance(currentLocale);

此BreakIterator确定字符串中的位置，文本可以在下一行中断开以继续。 BreakIterator检测到的位置是潜在的换行符。屏幕上显示的实际换行符可能不一样。

以下两个示例使用 BreakIteratorDemo.java 的 markBoundaries 方法显示BreakIterator检测到的线边界。 markBoundaries方法通过在目标字符串下打印插入符号（^）来指示行边界。

根据BreakIterator，在一系列空白字符（空格，制表符，换行符）终止后出现行边界。在以下示例中，请注意您可以在检测到的任何边界处断开线：

  1. She stopped.  She said, "Hello there," and then went on.
  2. ^   ^         ^   ^     ^      ^     ^ ^   ^    ^    ^  ^

在连字符后立即发生潜在的换行：

  1. There are twenty-four hours in a day.
  2. ^     ^   ^      ^    ^     ^  ^ ^   ^

下一个示例使用名为formatLines的方法将一长串文本分成固定长度的行。此方法使用BreakIterator来定位潜在的换行符。 formatLines方法简短，并且由于BreakIterator，与语言环境无关。这是源代码：

  1. static void formatLines(
  2.     String target, int maxLength,
  3.     Locale currentLocale) {
  5.     BreakIterator boundary = BreakIterator.
  6.         getLineInstance(currentLocale);
  7.     boundary.setText(target);
  8.     int start = boundary.first();
  9.     int end = boundary.next();
  10.     int lineLength = 0;
  12.     while (end != BreakIterator.DONE) {
  13.         String word = target.substring(start,end);
  14.         lineLength = lineLength + word.length();
  15.         if (lineLength >= maxLength) {
  16.             System.out.println();
  17.             lineLength = word.length();
  18.         }
  19.         System.out.print(word);
  20.         start = end;
  21.         end = boundary.next();
  22.     }
  23. }

BreakIteratorDemo程序调用formatLines方法如下：

  1. String moreText =
  2.     "She said, \"Hello there,\" and then " +
  3.     "went on down the street. When she stopped " +
  4.     "to look at the fur coats in a shop + "
  5.     "window, her dog growled. \"Sorry Jake,\" " +
  6.     "she said. \"I didn't know you would take " +
  7.     "it personally.\"";
  9. formatLines(moreText, 30, currentLocale);

此调用formatLines的输出是：

  1. She said, "Hello there," and
  2. then went on down the
  3. street. When she stopped to
  4. look at the fur coats in a
  5. shop window, her dog
  6. growled. "Sorry Jake," she
  7. said. "I didn't know you
  8. would take it personally."