Writing a conditional statement

Question

I am a student learning Java and am stuck on the last part of a homework problem. I need to write a conditional statement that prints whether the roll of the dice was a Yahtzee or not (all five dice are equal to one another). I cannot figure out how to do this since I used ints and not boolean. I know I cannot cast an int into boolean and up to this point this casting is the only way I know how to change variables. Any help would be appreciated since the ways to achieve what I am looking for have been more than I can understand at this point. This is what I have and the issue is in the second to last line.

import java.util.Random;

public class FiveDice_JLR
{
   //-----------------------------------------------------------------
   //  Generates random numbers in various ranges.
   //-----------------------------------------------------------------
   public static void main(String[] args)
   {
      Random generator = new Random();
      int die1, die2, die3, die4, die5;

      die1 = generator.nextInt(6)+1;
      System.out.println("Die 1: " + die1);

      die2 = generator.nextInt(6)+1;
      System.out.println("Die 2: " + die2);

      die3 = generator.nextInt(6)+1;
      System.out.println("Die 3: " + die3);

      die4 = generator.nextInt(6)+1;
      System.out.println("Die 4: " + die4);

      die5 = generator.nextInt(6)+1;
      System.out.println("Die 5: " + die5);


      **if(die1==die2&==die3==die4&==die5&&);**
      {
      System.out.println("Yahtzee!!!!");
      }

   }

Answer 1

If you use just &, that is the bitwise AND, therefore it compares the bits of all the numbers. What you want is &&, which is logical AND:

if(die1 == die2 && die2 == die3 && die3 == die4 && die4 == die5) {
    // Something here...
}

Also note that each && operator just like the == operator, requires 2 operands to properly compare

---

Assuming all your values are positive, another method to check if all numbers are equal to each other is to add them all up and check if the sum is equal to 5 times one of the values.

if((die1 + die2 + die3 + die4 + die5) == die1 * 5) {
    // Something here...
}

This is doing the same thing and is shorter, but is prone to error because you may in the future decide to generate negative numbers (for some reason), or decide to use more dice and forget to change 5 to the appropriate number, etc. In general, just stick to the first one

Answer 2

There are two operators that will be important for checking that the values of all your dice are the same: the conditional AND operator (&&) and the equality operator (==). The Java documentation includes some good details of what these are, and how to use them.

There are a couple of things to keep in mind with these. Both of these operators are binary operators. They operate on two operands. e.g. a == b compares the value of a to b. Similarly, a && b evaluates to true if both a and b are true.

Of course, this presents a challenge when we want to compare the values of more than two operands. Say we have three variables, a, b, and c. How would we check that they all have the same value? (For simplicity, we'll assume they're all primitive types).

We know how to check that a and b are the same: a == b.

We also know how to check that b and c are the same: b == c.

If both of these are true then, by the transitive property of equality, we know that a must also be equal to c. How do we check two conditions within a single statement? Using the conditional AND operator, of course:

a == b && b == c

This was a simple example with just three variables, but this can be extended to any number of variables (say, to the values of 5 dice). Give it a try, and see if you can get it working using these two operators.

Answer 3

The statement you are looking for is

if(die1==die2 && die2==die3 && die3==die4 && die4==die5)

Or, for @smac89's and &duffymo's benefit, a version with &:

if(die1==die2 & die2==die3 & die3==die4 & die4==die5)

which will run slower because of fully evaluating everything, but is otherwise semantically identical.