java - Matcher.lookingAt() 和 find() 有什么区别？

Question

我正在看 Java 正则表达式教程，标题本身就很清楚了。看起来 Matcher.lookingAt() 正在尝试匹配整个字符串。是真的吗？

Answer 1

documentation for Matcher.lookingAt清楚地解释了 lookingAt 尝试匹配的区域:

Like the matches method, this method always starts at the beginning of the region; unlike that method, it does not require that the entire region be matched.

所以不，lookingAt 不需要匹配整个字符串。那么lookingAt和find有什么区别呢？来自Matcher Javadoc overview :

• The matches method attempts to match the entire input sequence against the pattern.
• The lookingAt method attempts to match the input sequence, starting at the beginning, against the pattern.
• The find method scans the input sequence looking for the next subsequence that matches the pattern.

lookingAt 总是从头开始，但是 find 会扫描起始位置。

从另一个角度看，matches 有一个固定的开始和结束，lookingAt 有一个固定的开始但一个可变的结束，find 有一个可变的开始和结束。