public class Zahl {

     private String type;
     private int val;
     private int val2;

     public Zahl(String type, int val) {
         this.type = type;
         this.val = val;
     }

     public Zahl(String type, int val, int val2) {
         this.type = type;
         this.val = val;
         this.val2 = val2;
     }

     public double getDoubleVal() {
         switch (type) {
         case "bruch":
             return val / (double) val2;
         case "wurzel":
             return Math.sqrt(val);
         }
         return 0;
     }

     //Testprogramm
     public static void main(String[] args) {
         Zahl[] z = new Zahl[2];
         z[0] = new Zahl("bruch",1,2);  //1/2  (Bruch)
         z[1] = new Zahl("wurzel",2);   //sqrt(2) (Wurzel)
         for (Zahl a: z) {
             System.out.println(a.getDoubleVal());
         }
     }
}