在对象上调用方法 Java

Question

I'm taking an introduction to java programming course at university and have an exam next week. I'm going through past exam papers am sort of stuck on this question:

Consider the following class X: class X { private boolean a; private int b; ... } 

(i)     Write a constructor for this class. [2 marks] 


(ii)   Show how to create an object of this class. [2 marks] 


(iii)  Add a method out, which returns b if a is true, and -b otherwise. This method must be usable for any client of 
    this class. [2 marks] 

I've included my code below, but what i'm stuck on is in the final part to this question. How does one call a method on a new object (as we haven't been taught that in class)? Or, does the question imply that the method has to be usable with any object, not just the created object?

Sorry for my awful code and dumb question, i'm really struggling with Java.

public class X {
 private boolean  a;
 private int b;

 X(final boolean i, final int j) {
  a = i;
  b = j;

 }

 static int Out(boolean a, int b) {
 if (a == true) {
  return b;
 }
  return -b;
 }

 public static void main(String[] args) {;

 X object1 = new X(true, 5);

 System.out.println(Out(object1));


 }
}

Answer 1

You're very close to the solution. Simply make a method like this:

public int out() {
    if (a) {
        return b;
    } else {
        return -b;
    }
}

Then you can call it in your main method like this:

X object1 = new X(true, 5);
System.out.println(object1.out());

NB: remove the semicolon at the end of public static void main(String[] args) {;

Answer 2

I think you were meant to create a non-static method named out , which can be called by the client of the class (any place where you create a new object of type X ) using the dot notation

public int out() {
   if(a)
      return b;
   else
      return -b;
}

public static void main(String[] args) {
   X object1 = new X(true, 5);
   int result = object1.out();
   System.out.println(result);
}