boolean method trouble

Question

Im trying to implement a method to return the boolean true or false. The method initializes the boolean isMatch to true or false based on the if and else statement.

public class BooleanTest {
   int num;
   boolean isMatch;

   public BooleanTest() {
     num = 10;
   }

   public boolean isMatch() { //variable is already initialize to 10 from constructor
     if (num == 10)
       isMatch = true;
     else
       isMatch = false;
     return isMatch;
   }

   public static void main(String[] arg) {
     BooleanTest s = new BooleanTest();

     System.out.println(s.isMatch);
   }
} 

The outprint of isMatch should be true, but i get the output isMatch is false. Is my boolean method wrong and how can i fix it? Thank you for your help.

Answer 1

Firstly, your entire isMatch method would be better collapsed to:

public boolean isMatch() {
    return num == 10;
}

Secondly, your existing code really will work, unless you're changing the value of num. You should look at whatever diagnostics you're using to show the output as false... I suspect they're misleading you. Is it possible that you're printing out the value of the field called isMatch rather than calling the method? That would explain it. This is one reason why it's a bad idea to have a method with the same name as a field. Additionally, I'd recommend making your fields private.

Short but complete example showing both the working method call and the "failed" field access (working fine, but not doing what you want):

public class BooleanTest {
    private int num;
    private boolean isMatch;

    public BooleanTest() {
        num = 10;
    }

    public boolean isMatch() {
        return num == 10;
    }

    public static void main(String[] args) {
        BooleanTest test = new BooleanTest();
        System.out.println(test.isMatch()); // true
        System.out.println(test.isMatch); // false
    }
} 

It's not clear why you've got the field at all, to be honest - I'd remove it.