Using operators with objects in Java

Question

Let's say we have a class as follows:

public class Time{
 int hour;
 int min;
 Time(int hour,int m){
  hour=h;
  min=m;
 }
 public String toString(){
 return hour+":"+min;
 }
}

And I want to write some code like this in main with results as in the comments:

Time t1 = new Time(13,45);
Time t2= new Time(12,05);
System.out.println(t1>=t2); // true
System.out.println(t1<t2);  // false
System.out.println(t1+4);   // 17:45
System.out.println(t1-t2);  // 1:40
System.out.println(t1+t2);  // 1:50 (actually 25:50)
System.out.println(t2++);   // 13:05

Can I do that by interfaces etc. or the only thing I can do is to write methods instead of using operators?

Thanks in advance.

Answer 1

That's called operator overloading, which Java doesn't support: Operator overloading in Java

So yes, you have to stick with methods.

EDIT: As some comments have said, you can implement Comparable to make your own compareTo method https://stackoverflow.com/a/32114946/3779214

Answer 2

You simply cannot. You cannot overload an operator. You need to write methods in to supports those operators.

Instead of writing methods in Time, I suggest you to write util methods.

For ex:

System.out.println(TimeUtil.substract(t1,t2));