Generate Random Number and String in Java

In this post we will see different methods of generate random number and String in Java.

Generate Random Number in java

Logic 1- Using Random class

package demopkg;

import java.util.Random;

public class GenRandomNumber {
    
    
    public static void main(String[] args) {
        
        //Logic 1 - Using Random class
        
        Random rand = new Random();
        int random_num=rand.nextInt(100);
        System.out.println(random_num);
        
        
    }

}

Code Explanation:

Random is a class. nextInt () is a method by using we can generate random number.

Note:  There are so many methods in Random class like – nextDouble(), nextFloat(), nextBoolean(), nextLong() etc.  to generate the random number.

Logic 2 – Using Math class

package demopkg;

import java.util.Random;

public class genRandomNumber2 {
    
public static void main(String[] args) {
        
        //Logic 2 - Using Math class
        
        System.out.println(Math.random());
        
        
    }


}

Code Explanation:

Math is a class. random()  is a static method by using we can generate double format random number.

Logic 3 – Generate random alphanumeric string in java

package demopkg;

import org.apache.commons.lang3.RandomStringUtils;

public class GenRandomAlphbeticString {
    
    public static void main(String[] args) {
        
        // Logic 3- Apache commons API
        // Generate random numeric 
        String randNum = RandomStringUtils.randomNumeric(4);
        System.out.println(randNum);
        
        
        // Generate random String
        String randStr = RandomStringUtils.randomAlphabetic(5);
        System.out.println(randStr);
        
    }

}

Code Explanation:

First we need to download Apache commons lang API jars from here – Then import into your project.

There is a RandomStringUtils class which have different methods like randomNumeric(), randomeAlphabetic() etc.

How to Generate Random Characters in Java

Read this link – Generate Random Characters