How to find out if a substring of a Java string matches a regular expression?

Question

The Java String class has a matches(String regex) method that checks whether the current string matches the given regular expression. However, how can we find whether a substring of the current string would match the regular expression?

I am trying to mimic the behavior of grep using Java. grep takes a line and prints all those lines that match the given regular expression anywhere in the line. I am not sure how to do that with Java, because the matches method checks whether the entire line (ie string) matches the regex and not any substring within it.

Answer 1

Matcher#find()方法Matcher#find()您的需求

Answer 2

就像ColinD所说的那样，最好的选择是一次在字符串中读一行，然后在两端都使用一个不愿意的通配符来运行正则表达式。

Answer 3

You can modify the regular expression to allow wildcards at the front and back of the string.

So instead of:

Pattern regex = Pattern.compile("hello\\sworld")

you have

Pattern regex = Pattern.compile(".*hello\\sworld.*);