Regex in Java (Pattern, Matcher)

reg.java

//----------------------------------code 1-----------------------------
package testPackage;
import java.util.*;
import java.util.regex.Pattern;

import jdk.internal.org.objectweb.asm.commons.TryCatchBlockSorter;

import java.io.*;
import java.lang.*;
import java.math.*;
class Test{
	
	public static void main(String[] args) {
		Scanner input=new Scanner(System.in);
		String IP=input.nextLine();
		System.out.println(IP.matches(new MyRegex().pattern));
		// IP address example
		// 000.12.12.234
		//ip==A.B.C.D, A.length<=3, A<=255 and all are numbers
		
	}
}
class MyRegex{
	String zero="([0-9]|[0-9][0-9]|(0|1)[0-9][0-9]|2[0-4][0-9]|25[0-5])";
	String pattern=zero+"."+zero+"."+zero+"."+zero;
}
//----------------------------------code 2-----------------------------------------
/*
    1) \\d{1,2} catches any one or two digit number
    2) (0|1)\\d{2} catches any three digit number starting with 0 or 1.
    3) 2[0-4]\\d catches numbers between 200 and 249.
    4) 25[0-5] catches numbers between 250 and 255.
*/
/*
    1-9, 01-09, 10-99 --> \d{1,2}
    000-009, 010-099, 100-199 --> {0|1}\d{2}
    200-249 --> 2[0-4]\d
    250-255 --> 25[0-5]
    \d <=> [0-9]
*/
/*
	More on Rgex : 
	import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.management.Query;

import java.lang.*;
import java.lang.*;
import java.lang.*;
import java.awt.List;
import java.io.*;
import java.time.*;
import java.math.*;
import java.rmi.Remote;
import java.sql.Array;
//demostration of Pattern and Matcher in java
public class MyClass {
	
	public static void main(String[] args)throws java.lang.Exception{
		//Scanner input=new Scanner(System.in);
		//1
		System.out.println(Pattern.matches("ge*pra*kas*hw", "geekpraakashw"));
		//2
		Pattern pat=Pattern.compile("geeks");
		Matcher m=pat.matcher("geeksforgeeks");
		while(m.find()){
			System.out.println("pattern found from "+m.start()+" to "+ m.end());
		}
		//3. Java program to demonstrate Case Insensitive Searching
		Pattern p=Pattern.compile("ge*", Pattern.CASE_INSENSITIVE);
		Matcher m1=p.matcher("geeksforgeeks.org");
		while(m1.find()){
			System.out.println("pattern found from +"+m1.start()+" to "+m1.end());
		}
		//4. Java program to demonstrate working of split() to split a text based on a delimiter pattern
		String text="geeks1for2geeks3web";
		String delim="\\d";
		String[] s=text.split(delim);
		for(String ans : s){
			System.out.println(ans);
		}
		
		
		
	}
	
}
//-----------------------------------code 3-------------------------------------------------
*/
/*
	// HTML Extractor using Regex (although, it's not suggested, however)
	import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.management.Query;

import java.lang.*;
import java.lang.*;
import java.lang.*;
import java.awt.List;
import java.io.*;
import java.time.*;
import java.math.*;
import java.rmi.Remote;
import java.sql.Array;
//demostration of Pattern and Matcher in java
public class MyClass {
	
	public static void main(String[] args)throws java.lang.Exception{
		Pattern r=Pattern.compile("<(.+?)>([^<>]+)</\\1>");
		Scanner input=new Scanner(System.in);
		int test=Integer.parseInt(input.nextLine());
		int count=0;
		while(test-- >0){
			count=0;
			String line=input.nextLine();
			Matcher m=r.matcher(line);
			while(m.find()){
				System.out.println(m.group(2));
				count++;
			}
			if(count==0){
				System.out.println("None");
			}
		}
		
	}
	
}

/*