For Loop Help

[nekromantik]

Hi
I been trying to figure out this problem for last few days but cannot find the answer.
I am trying to use nested for loops to try and create a 6 character string using letters/numbers from a array. I need it so that it starts off with one character and then adds one more etc. Then need it to stop when it finds the word that has been inputted.

Example is
a
b
..z
then
aa
ab
ac
...az

or even

a
z
aa
ba
za etc

thanks

[henryswanson]

I'm not quite sure what you're trying to do. Are you trying to make a random 6 character string from the characters in the array? You could do:

public static void main(String[] args) {
	char[] myCharacters = {'a', 'b', 'c', 'd', 'e'};
	Random r = new Random();
	String s = "";
	for(int i = 0; i < 6; i++) {
		int nextIndex = r.nextInt(myCharacters.length);
		char nextChar = myCharacters[nextIndex];
		s += nextChar;
	}
	System.out.println(s);
}

[themoffster]

try to get it outputting:
aa
ab
ac
...
az
ba
...
bz

once you've got that have a think about how in the first loop you could export a blank before the initaial 'a'

[nekromantik]

thanks guys
but got it working a very messy way

char[] letters = { 
          'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
         's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0','1','2','3','4','5','6','7','8','9',
      };
      boolean found = false;
      char[] guess = new char[7];
      int pos = 0, i = 0;
      String pass, guess1, guess2, guess3;
       loop:

           
  while (found == false) {
       
         
            for (int a = 0; a<36; a++){


            guess[0] = letters[a];


            pass = String.valueOf(guess);

            SHA1.SHA1(pass);

           System.out.println(pass);

             if (SHA1.hash == null ? hex == null : SHA1.hash.equals(hex)) {
             System.out.println("Found " + pass);
             found = true;

                }}
                
             for (int a = 0; a<36; a++){

             for (int b = 0; b<36; b++){
          
             guess[0] = letters[a];
              guess[1] = letters[b];


     pass = String.valueOf(guess);

      SHA1.SHA1(pass);

      System.out.println(pass);

       if (SHA1.hash == null ? hex == null : SHA1.hash.equals(hex)) {
         System.out.println("Found " + pass);
         found = true;
        
                 }}}

etc

now Im having another issue, the words it creates dont have the same SHA1 hash as the inputed word even though they are both the same word strings.

[Xeel]

Actually it's not that messy, the original solution for the problem also compares hashed values instead of strings. As for the problem check the strings you compare and the SHA method you use. If it still fails the problem is in the SHA method, then use manual implementation instead:

public static String sha1Enc(String str){
    char s[] = null;
    try{
        MessageDigest md5 = MessageDigest.getInstance("SHA");
        char alphabet[] = "0123456789abcdef".toCharArray();
        byte pwdBytes[] = md5.digest(str.getBytes());
        s = new char[pwdBytes.length<<1];

        for(int i=0, j=0; i<pwdBytes.length; i++){
            s[j++] = alphabet[(pwdBytes[i]&0xf0)>>4];
            s[j++] = alphabet[pwdBytes[i]&0xf];
        }
    }catch(NoSuchAlgorithmException e){
        e.printStackTrace();
    }
    return new String(s);
}

[nekromantik]

thanks I figured it out, it was because I had a array of 6 and when I converted it to string when it had less then 6 chars it created a String with spaces in it.

Whats the best way to end all 6 for loops when it finds a match?
I tried putting a while found == false at the start but it keeps on doing the inner loops even after it finds a match even though it sets it to found = true once a match is found.

[Xeel]

That happens because the expression in while is getting evaluated every time you iterate through it but not instantly after changing the value from the expression. So the loops you have inside the while are considered to be the same iteration pass.

To stop immediately the execution process use the labeled break statement. The difference can be easily seen in this example:

public static void main(String[] args){

    boolean myvar;
    int i;
    
    myvar = true;
    i=0;
    
    while(myvar){
        for(i=0; i<21; i++){
            if(i==10){
                myvar = false;
            }
        }        
    }
    System.out.println("i="+i); //prints out '21'
    
    
    myvar = true;
    i=0;
    
    mywhilelabel:while(myvar){
        for(i=0; i<21; i++){
            if(i==10){
                myvar = false; //not even necessary since the 'break' will stop the loop before the while condition is evaluated
                break mywhilelabel;
            }
        }
    }
    System.out.println("i="+i); //prints out '10'
}

[nekromantik]

edit

fixed it thanks