NegativeRegexTest.java

import org.junit.Test;

import java.util.regex.Pattern;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

public class NegativeRegexTest {


    @Test
    public void shouldTest() throws Exception {
        final Pattern pattern = Pattern.compile("\\{\"title\":\"(.*)\",\"firstName\":\"((?!john).*)\"\\}");

        assertTrue(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"Jeff\"}").matches());
        assertTrue(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"stubby4j\"}").matches());
        assertTrue(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"jon\"}").matches());
        assertTrue(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"anything but john\"}").matches());

        assertFalse(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"john of everything\"}").matches());
        assertFalse(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"john\"}").matches());
        assertFalse(pattern.matcher("{\"title\":\"Ms\",\"firstName\":\"john of Denmark\"}").matches());
    }
}