random string generator java

1import java.util.Random;
2
3public class Generator {
4	public static String generateRandomPassword(int len) {
5		String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijk"
6          +"lmnopqrstuvwxyz!@#$%&";
7		Random rnd = new Random();
8		StringBuilder sb = new StringBuilder(len);
9		for (int i = 0; i < len; i++)
10			sb.append(chars.charAt(rnd.nextInt(chars.length())));
11		return sb.toString();
12	}
13}

1public static String getRandomString(int size) {
2  	// The string that we will return
3	String rand = "";
4  	// The chars that are used to generate the random string
5	String chars = "1234567890-=!@#$%^&*()_+qwertyuiop[]\\QWERTYUIOP{}|asdfghjkl;'ASDFGHJKL:\"zxcvbnm,./ZXCVBNM<>?";
6  	// Loop based on the requested size
7  	for (int i = 0; i < size; i++) {
8      	// Add a random char from the chars string to the rand string
9		rand += chars.toCharArray()[new Random().nextInt(chars.length())];
10	}
11  	// Return the random string
12	return rand;
13}

1RandomStringUtils.randomAlphanumeric(17).toUpperCase()

1@Test
2public void givenUsingJava8_whenGeneratingRandomAlphanumericString_thenCorrect() {
3    int leftLimit = 48; // numeral '0'
4    int rightLimit = 122; // letter 'z'
5    int targetStringLength = 10;
6    Random random = new Random();
7 
8    String generatedString = random.ints(leftLimit, rightLimit + 1)
9      .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
10      .limit(targetStringLength)
11      .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
12      .toString();
13 
14    System.out.println(generatedString);
15}
16

1@Test
2public void givenUsingJava8_whenGeneratingRandomAlphabeticString_thenCorrect() {
3    int leftLimit = 97; // letter 'a'
4    int rightLimit = 122; // letter 'z'
5    int targetStringLength = 10;
6    Random random = new Random();
7
8    String generatedString = random.ints(leftLimit, rightLimit + 1)
9      .limit(targetStringLength)
10      .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
11      .toString();
12
13    System.out.println(generatedString);
14}