solucao do problema de soma 15 de forma aleatoria

gistfile1.java

class Cubo {
  
    int[] num = {1,2,3,4,8,6,7,5,9};
    int t = 0;
  
    public static void main (String args[]){
      new Cubo();
    }
    
    Cubo(){
      while(!calcula()){
          int aux1 = ( int ) Math.floor( ( Math.random() * 9 ) );
          int aux2 = ( int ) Math.floor( ( Math.random() * 9 ) );

           int a = num[aux1];
           num[aux1] = num[aux2];
           num[aux2] = a;
      }
    }
    
    private boolean calcula(){
      t++;
      if(
        ((num[0]+num[1]+num[2]) == 15) &&
        ((num[3]+num[4]+num[5]) == 15) &&
        ((num[6]+num[7]+num[8]) == 15) &&
        ((num[0]+num[4]+num[8]) == 15) &&
        ((num[2]+num[4]+num[6]) == 15) &&
        ((num[0]+num[3]+num[6]) == 15) &&
        ((num[1]+num[4]+num[7]) == 15) &&
        ((num[2]+num[5]+num[8]) == 15)){
          imprimir();
          return true;
        }
      //imprimir();
      return false;
      
    }
    
    private void imprimir(){
      for(int i=0; i < 9; i++){
        System.out.print("\t"+num[i]);
        if(i == 2 || i == 5 || i == 8){
          System.out.println("");
        }
      }
      System.out.println("--- Tentativa "+t+"\n\n\n");
    }
}