java - 关于 requireEnd Matcher 方法的说明

Question

直接来自 this Java API:

public boolean requireEnd()

Returns true if more input could change a positive match into a negative one.

If this method returns true, and a match was found, then more input could cause the match to be lost. If this method returns false and a match was found, then more input might change the match but the match won't be lost. If a match was not found, then requireEnd has no meaning.

Returns: true iff more input could change a positive match into a negative one.

我在网上找不到任何具体的例子。

有人可以向我展示它的使用示例吗？
提前致谢。

Answer 1

让我们以这个简单的例子为例:

public static void main(final String... args)
{
    final Pattern p = Pattern.compile("cat$");

    final Matcher m = p.matcher("I have a cat");
    m.find(); // finds a match
    System.out.println(m.requireEnd()); // prints true
}

正则表达式的末尾有一个 anchor ；文档说，如果给出更多输入，它“[...] 可能会导致匹配丢失”。的确。考虑这个输入:

"I have a catflap"

正则表达式在这里不再匹配:匹配丢失。

如果现在我们替换 "cat$"与 "cat"然后 .requireEnd()会返回 false :使用上面的输入， cat仍然会被正则表达式引擎匹配。