Generate a random string in Java

Question

I want to generate a 6 character random string on every compilation of a program in Java.

For example: AXFGCD, GDGXSD, PLRSFX, GLTSDL

public class generate{
    public static void main(String args[]){
        generate();
    }

    string word = "";
    string Characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    void generate(int x){
        if (x==7) return;

        int time = System.currentTimeMillis() % 33; //to generate time in mili second
        word += characters.charAt(time);
        System.out.println(time);
        return generate(++x);
    }
}

output is

A,AX,AXF,AXFC,AXFCG,AXFCGA

but I want direct 6 digit word

And to be pedantic - though I'm sure you don't care - this is generated at run time and not compile time. — Michael, Oct 12 '17 at 08:32
@rohitjoshi9023 Do not edit a question with a code fix. If the code is broken somehow, raise that as a comment or as an answer. — Michael, Oct 12 '17 at 08:35
Possible duplicate of [How to generate a random alpha-numeric string?](https://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string) — haindl, Oct 12 '17 at 08:47

Dinh · Answer 1 · 2017-10-12T08:47:56.540

This was written in Notepad++ as I currently dont have any IDE available, I hope this compiles and if it does it should work :) If you want to use uppercase characters simply edit the for loop!

public class generate{

    private static char[] characters;
    private static Random random = new Random();

    public static void main(String args[]){
        characters = new char[26];
        int index = 0;
        for (char c = 'a'; c <= 'z'; c++) {
            characters[index++] = c;
        }
        System.out.println(generate());
    }

    static String generate() {
        String word = "";
        for(int i = 0 ; i < 7 ; i++) {
            word += Character.toString(characters[random.nextInt(characters.length)]);
        }
        return word;
    }
}

Edit: using your code!

public class generate{
    public static void main(String args[]){
        generate();
    }

    string word = "";
    string Characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    void generate(int x){
        if (x==7) {
            System.out.println(word);
            return;
        }

        int time = System.currentTimeMillis() % 33; //to generate time in mili second
        word += characters.charAt(time);
        return generate(++x);
    }
}

Turtle · Answer 2 · 2017-10-12T08:36:52.293

Your method is achieving your purpose. Your problem is that you are "logging" your steps by printing them in your method (Also, there are errors like string, calling your generate funciton incorrectly, but since you gave us the output I guess you fixed it at some point).

If you just do this:

public class generate{
    public static void main(String args[]){
        generate(0);
        System.out.println(word); // Here word is complete

    }

    String word = "";
    String Characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    void generate(int x){
        if (x==7) return;

        int time = System.currentTimeMillis() % 33; //to generate time in mili second
        word += characters.charAt(time);
        return generate(++x);
    }
}

it will work. Alternatively, to print your word in your function, you could've use an iterative approach:

void generate(){
    for (int i = 6; i --> 0;) {
        int time = System.currentTimeMillis() % 33; //to generate time in mili second
        word += characters.charAt(time);
    }
    System.out.println(word);
}

Generate a random string in Java

2 Answers2