Trail: Internationalization
Lesson: Working with Text
Section: Detecting Text Boundaries

行边界

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。你可以使用 getLineInstance 方法创建的 BreakIterator 找到这些换行符或边界：

BreakIterator lineIterator =
    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 方法来显示检测到的行边界 BreakIterator。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，请注意你可以在检测到的任何边界处断开行：

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

在连字符后立即发生潜在的换行：

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

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：

static void formatLines(
    String target, int maxLength,
    Locale currentLocale) {

    BreakIterator boundary = BreakIterator.
        getLineInstance(currentLocale);
    boundary.setText(target);
    int start = boundary.first();
    int end = boundary.next();
    int lineLength = 0;

    while (end != BreakIterator.DONE) {
        String word = target.substring(start,end);
        lineLength = lineLength + word.length();
        if (lineLength >= maxLength) {
            System.out.println();
            lineLength = word.length();
        }
        System.out.print(word);
        start = end;
        end = boundary.next();
    }
}

BreakIteratorDemo 程序调用 formatLines 方法，如下所示：

String moreText =
    "She said, \"Hello there,\" and then " +
    "went on down the street. When she stopped " +
    "to look at the fur coats in a shop + "
    "window, her dog growled. \"Sorry Jake,\" " +
    "she said. \"I didn't know you would take " +
    "it personally.\"";

formatLines(moreText, 30, currentLocale);

此调用 formatLines 的输出是：

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