CODEWITHSUNDEEP
javaarraysrandom
kasper_341
kasper_341

Reputation: 95

generate random lower case letter : ERROR

i am getting an unexpected output to generate lower case random letters - my code is 

public class CountLettersInArrayDemo {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    CountLettersInArray ca = new CountLetterInArray();

    char [] chars;

    chars = ca.setCreateArray();
    System.out.println(chars);

public class CountLettersInArray {

CountLettersInArray()
{}
//method to create an array
public char[] setCreateArray()
{
    //declare an array
    char [] chars = new char[100];
    //initialize an array with random characters

    for (int i=0;i<chars.length;i++)
    {
        chars[i]=(char)('a' + Math.random() * ('z' + 'a' -1));          
    }
    return chars;
}
}

output is -

uěýyĬõĒēÕø»İäĂº±«Ċþÿd¢¼Ęÿuìăi±vÞ´Ĥč°ĩĒôĵ¶âþĂđďäÄĮÝă¤yÎĪÊíÆĭ××môÓâ¢ÓġÓÙĊïĺv×ĺî÷dĤĸt

Q: any ideas where the mistake is ? thanks

Upvotes: 1

Views: 8491

Answers (6)

Zoran Janjic
Zoran Janjic

Reputation: 121

How about this option: ( a+ Math.random() * b) - return a random number between a and a+b, excluding a+b 'a'to'z' Decimal value: 97 to 122;

Random rand = new Random();
char a  = (char) (97+(int)(Math.random()*25));
System.out.println(a);

Upvotes: 0

piotrek
piotrek

Reputation: 14550

don't reinvent the wheel. use commons-lang3

import static org.apache.commons.lang3.RandomStringUtils.randomAlphabetic;
...
randomAlphabetic(length).toLowerCase()

Upvotes: 0

Deepak Bhatia
Deepak Bhatia

Reputation: 6276

There is small problem associated with your code,
You are using chars[i]=(char)('a' + Math.random() * ('z' + 'a' -1));

Instead try this, 

for (int i=0;i<chars.length;i++)
{
    chars[i]=(char)('a' + Math.random() * ('z' - 'a') );          
}

or a little faster way, 

char Diff = 'z' - 'a';
for (int i=0;i<chars.length;i++)
{
    chars[i]=(char)('a' + Math.random() * Diff);          
}

Just EXPLANATION You are trying to generate integers between a range using the simple formula,

Min + (int)(Math.random() * ((Max - Min) + 1))

But in your code you have made a small mistake Max + Min instead of Max - Min

Upvotes: 1

KhAn SaAb
KhAn SaAb

Reputation: 5376

try this.it will generate 8 characters random String

public String randomString() {
    int len = 8;
    String alphaNumericString = "abcdefghijklmnopqrstuvwxyz1234567890";

    // creating the object for string builder
    StringBuilder sb = new StringBuilder(len);


    try {

        String PASSSTRING = alphaNumericString;
        // creating the object of Random class
        Random rnd = new Random();
        for (int i = 0; i < len; i++) {
            // generating random string
            sb.append(PASSSTRING.charAt(rnd.nextInt(PASSSTRING.length())));
        }
    } catch (Exception e) {
    e.printStackTrace();
    }

    // returning the random string
    return sb.toString();
}// randomString()

Upvotes: 0

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136062

try this

  chars[i]=(char)('a' + Math.random() * ('z' - 'a'));

or simply 

  chars[i]=(char)('a' + Math.random() * 26);

Upvotes: 1

Toon Borgers
Toon Borgers

Reputation: 3658

What you could try is the following:

Random random = new Random();
for(int i = 0; i<chars.length;i++){
    chars[i] = (char)(random.nextInt('z'-'a') + 'a');
}

Upvotes: 0

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