import java.util.Random;    
import java.util.ArrayList;
public class test {
     public static void main(String[] args) {
   
        Random r = new Random();
        ArrayList ar = new ArrayList();
        int low = 20;
        int high = 60;
        int cislo = r.nextInt(high-low) + low;
        int odpocet=0;
        while(true){
            
            if (!ar.contains(cislo)) {
                ar.add(cislo);
                odpocet++;
            }
            if (odpocet==7) 
              break;  
            
        }
        
         for (int i = 0; i < ar.size(); i++) {
             System.out.print(ar.get(i)+"  ");
         }
     
     }
}

CHYBA H:/lessssss/test.java uses unchecked or unsafe operations.
Recompile with -Xlint:unchecked for details.