random number string generator java code example

Example 1: generate random string in java

import java.util.Random;

public class Generator {
	public static String generateRandomPassword(int len) {
		String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijk"
          +"lmnopqrstuvwxyz!@#$%&";
		Random rnd = new Random();
		StringBuilder sb = new StringBuilder(len);
		for (int i = 0; i < len; i++)
			sb.append(chars.charAt(rnd.nextInt(chars.length())));
		return sb.toString();
	}
}

Example 2: Random number generator in java

// java.util.random example
import java.util.Random;
public class JavaRandomClass
{
   public static void main(String[] args)
   {
      Random random = new Random();
      // random integers in range 0 to 999 
      int randInt1 = random.nextInt(1000); 
      int randInt2 = random.nextInt(1000);
      // printing random integers
      System.out.println("Random Integers: " + randInt1); 
      System.out.println("Random Integers: " + randInt2);
      // here we are generating Random doubles
      double randDou1 = random.nextDouble(); 
      double randDou2 = random.nextDouble();
      // printing random doubles
      System.out.println("Random Doubles: " + randDou1); 
      System.out.println("Random Doubles: " + randDou2);
   }
}

Example 3: java 8 random string generator

@Test
public void givenUsingJava8_whenGeneratingRandomAlphanumericString_thenCorrect() {
    int leftLimit = 48; // numeral '0'
    int rightLimit = 122; // letter 'z'
    int targetStringLength = 10;
    Random random = new Random();
 
    String generatedString = random.ints(leftLimit, rightLimit + 1)
      .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
      .limit(targetStringLength)
      .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
      .toString();
 
    System.out.println(generatedString);
}