With this example we are going to demonstrate how to use Matcher.lookingAt() API method to match an input sequence, starting at the beginning of the input, against a specified pattern. In short, to match a Sting input against a pattern with Matcher.lookingAt() API method you should:

• Compile a String regular expression to a Pattern, using compile(String regex) API method of Pattern.
• Use matcher(CharSequence input) API method of Pattern to create a Matcher that will match the given String input against this pattern.
• Use lookingAt() API method of Matcher to match the input against the pattern, starting from the beginning of the input, but without requiring that the entire region be matched.
• Reset the matcher with a new input sequence with reset(CharSequence input) API method to match a new String input against the pattern.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;

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

public class MatcherLookingAt {
    
  public static void main(String args[]) {


    Pattern pattern = Pattern.compile("J2SE");

    String str1 = "J2SE is the only one for me";
    String str2 = "For me, it's J2SE, or nothing at all";
    String str3 = "J2SEistheonlyoneforme";

    Matcher m = pattern.matcher(str1);

    String msg = ":" + str1 + ": matches?: ";
    System.out.println(msg + m.lookingAt());
    m.reset(str2);

    msg = ":" + str2 + ": matches?: ";
    System.out.println(msg + m.lookingAt());

    m.reset(str3);

    msg = ":" + str3 + ": matches?: ";
    System.out.println(msg + m.lookingAt());

  }
}

Output:

:J2SE is the only one for me: matches?: true
:For me, it's J2SE, or nothing at all: matches?: false
:J2SEistheonlyoneforme: matches?: true

 
This was an example of Matcher.lookingAt() API method in Java.