La seguente classe mi stampa 10 password uguali mentre io vorrei che venissero stampate 10 password differenti.
dove ho sbagliato?

codice:
import java.util.*;

public class PwdGenerator {

	public static void main(String[] args)
	{	
		String pwdGenerata = "";
		PwdGenerator pg=new PwdGenerator();
		for (int i=1;i<=10;i++) 
		{
			pwdGenerata=pg.getPWD();
			System.out.println("pwd:"+pwdGenerata);
			
		}

		
		

	}

    public PwdGenerator() {
           
    }
    
	
		
    public static String getPWD() {
        Random rnd = new Random();
        //decido dimensione password
        int dim = rnd.nextInt(5);
        dim = dim+6;
        //decido la quantità di cifre numeriche
        int num = rnd.nextInt(dim-4)+1;
        num= num+2;
        //decido la quantità di cifre alfa
        int alfa = dim-num;
        int appoggio=0;
        String pass="";
        int alterna=0;
        int contnum=1;
        int contalfa=1;
        for (int i=1;i<=dim;i++) {
            alterna = rnd.nextInt(2);
            if (contalfa>alfa){alterna=0;}
            else{if (contnum>num) {alterna=1;}
            }
            if (alterna==1) {contalfa++;
            appoggio = rnd.nextInt(25);
				switch (appoggio) {
					case 0 : pass = pass+"A";break;
					case 1 : pass = pass+"B";break;
					case 2 : pass = pass+"C";break;
					case 3 : pass = pass+"D";break;
					case 4 : pass = pass+"E";break;
					case 5 : pass = pass+"F";break;
					case 6 : pass = pass+"G";break;
					case 7 : pass = pass+"H";break;
					case 8 : pass = pass+"I";break;
					case 9 : pass = pass+"J";break;
					case 10 : pass = pass+"K";break;
					case 11 : pass = pass+"L";break;
					case 12 : pass = pass+"M";break;
					case 13 : pass = pass+"N";break;
					case 14 : pass = pass+"O";break;
					case 15 : pass = pass+"P";break;
					case 16 : pass = pass+"Q";break;
					case 17 : pass = pass+"R";break;
					case 18 : pass = pass+"S";break;
					case 19 : pass = pass+"T";break;
					case 20 : pass = pass+"U";break;
					case 21 : pass = pass+"W";break;
					case 22 : pass = pass+"X";break;
					case 23 : pass = pass+"Y";break;
					case 24 : pass = pass+"Z";break;
				}
            }
            if (alterna==0) {contnum++;
            appoggio = rnd.nextInt(10);
				switch (appoggio) {
					case 0 : pass = pass+"0";break;
					case 1 : pass = pass+"1";break;
					case 2 : pass = pass+"2";break;
					case 3 : pass = pass+"3";break;
					case 4 : pass = pass+"4";break;
					case 5 : pass = pass+"5";break;
					case 6 : pass = pass+"6";break;
					case 7 : pass = pass+"7";break;
					case 8 : pass = pass+"8";break;
					case 9 : pass = pass+"9";break;
				 }
            }
        }
        
        return pass;
    }
    
}