Thread: Homework Question

Consider the following code which is supposed to subtract a value passed to the method from an instance variable; however, there is a problem. Re-write this code, without renaming any variable names, to resolve the problem.
private int number = 542;
public void subtractNumbers (int number)
{
number = number - number;
System.out.println("The local variable is: " + number);
System.out.println("The instance variable is: " + number);
}

I don't need an answer to the problem, I just need to know where to start because I have no idea.

You have two variables with the same name, one is a class field and the other a parameter to a method, and you must tell the compiler which is which. You can specify the class field by preceding it with something -- do you know what it is you can use?

At first I thought I should make it a constant but that didn't work...

Originally Posted by EPC

At first I thought I should make it a constant but that didn't work...

Hint #2, you would precede one of the variables with <something>.number. Please fill in the blank: What is <something>?

I honestly have no idea.

--- Update ---

this?

--- Update ---

Thank you! But can you tell me what "this" does. I've gotten the correct answer but I've never seen "this" used before now.

Originally Posted by EPC

I honestly have no idea.

--- Update ---

this?

--- Update ---

Thank you! But can you tell me what "this" does. I've gotten the correct answer but I've never seen "this" used before now.

this.<identifier_name> specifies that the identifier is a field of the class since it belongs to "this", to the instance of the class. That is why often you'll see setter methods that look like so:

public void setFoo(int foo) {
   this.foo = foo;
}

The this.foo means a class field named "foo" is on the left hand side of the assignment while the parameter of the same name is on the right.