In this example we will show how to validate IP address with regular expression in Java.

Source Code

package com.beginner.examples;

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

public class ValidateIP {

	public static void main(String[] args) {
		String oneAddress = "10.127.30.45"; 
		String twoAddress = "127.30.45";
		String threeAddress = "255.255.255.2567";
		
		System.out.println(isIP(oneAddress));
		System.out.println(isIP(twoAddress));
		System.out.println(isIP(threeAddress));
	}
	
	public static boolean isIP(String addr){  
		if(addr.length()  15 || "".equals(addr))
		{  
			return false;
		}
		String rexp = "([1-9]|[1-9]d|1d{2}|2[0-4]d|25[0-5])(.(d|[1-9]d|1d{2}|2[0-4]d|25[0-5])){3}";  
		Pattern pat = Pattern.compile(rexp);     
		Matcher mat = pat.matcher(addr);    
		boolean ipAddress = mat.find();  
		return ipAddress;  
	}
}

Output:

true
false
false

References

Imported packages in Java documentation:

• Matcher
• Pattern