Regex Matcher for JUnit4 assertThat

RegexStringMatcher.java

import org.hamcrest.BaseMatcher;
import org.hamcrest.Description;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

class RegexStringMatcher extends BaseMatcher {
    private final Pattern mExpectedPattern;

    public RegexStringMatcher(String expected) {
        mExpectedPattern = Pattern.compile(expected);
    }

    public static RegexStringMatcher isMatch(String expected) {
        return new RegexStringMatcher(expected);
    }

    @Override
    public boolean matches(Object actual) {
        String actualStr = (String) actual;
        Matcher matcher = mExpectedPattern.matcher(actualStr);
        return matcher.find();
    }

    @Override
    public void describeTo(Description description) {
        description.appendText("pattern: ").appendText(mExpectedPattern.pattern());
    }
}