Question

Just out of curiosity! If I got a method that takes user input and stores it as an int variable. Is there a way I could pass those methods on to another method? I know about return values, but that is only (as far as I know) for one single number,object etc…

The easy way would of course to just to do calculate the result within this method, but is it possible somehow to pass these ints: a,b. To another method, without using global variables? I am just wondering.

private void takeInput(int valueA, int valueB){
    println("Enter a number: (a) and (b), to calculate the Phytagoeran Theorem: (c)\n");
    int a = readInt("a:");
    println("you set the value of a to: "+a +"\n\nNext! set the value of b");
    int b = readInt("b:");
    println("you set the value of b to:"+b);
}

Answer 1

The question is unclear, but I wonder whether you’ve invented “dependency injection”?

The first part of the puzzle is that, yes, a method can return more than one value, by wrapping them in an object.

public class ValuePair {
    public int a;
    public int b;
}

public ValuePair takeInput(){
  ValuePair pair = new ValuePair();
  println("Enter a number: (a) and (b)\n");
  pair.a = readInt("a:");
  pair.b = readInt("b:");
  return pair;
}

And with that you can do:

ValuePair p = takeInput();
System.out.println("Hypotenuse is " + calculateHypotenuse(p.a, p.b) + "\n";

(Note that public fields are not usually considered good style – I use them here because the code is shorter. In real code use getters and setters).

---

That might be all the answer you need. But you ask:

Is there a way I could pass those methods on to another method?

Well, yes you can if you wrap that method in a class dedicated the purpose. For reasons that I hope will become apparent, we’ll define an interface first.

 public interface ValuePairSource {
    public ValuePair getPair();
}

… and a class that implements it:

public class UserInputValuePairSource implements ValuePairSource {
    @Override
    public ValuePair getPair() {
         ValuePair pair = new ValuePair();
         println("Enter a number: (a) and (b)\n");
         pair.a = readInt("a:");
         pair.b = readInt("b:");
         return pair;
    }
}

Now you could create a Pythagoras class that can be told where to get its values.

public class Pythagoras {
     private ValuePairSource valuePairSource;

     public Pythagoras(ValuePairSource source) {
         this.valuePairSource = source;
     }

     public double hypotenuse() {
         ValuePair pair = valuePairSource.getPair();
         return Math.sqrt(pair.a ^ 2 + pair.b ^ 2)
     }
}

In the constructor, we tell each Pythagoras object we create, how to get a pair of values. So we can use it like this:

Pythagoras p = new Pythagoras(new UserInputValuePairSource());
double hypotenuse = p.hypotenuse();

What use is this? Well, it means we can invent other kinds of ValuePairSource. For example, a ShapeValuePairSource, which gets the values from a Shape object we set it up with.

(These are hypothetical classes for the purpose of the question)

So you might use it like this:

Triangle t = canvas.getLastTriangle(); // or whatever
ValuePairSource vps = new ShapeValuePairSource(triangle);
Pythagoras p = new Pythagoras(vps);
double hypotenuse = p.hypotenuse();

So without changing the Pythagoras class at all, we now have it reading the values from a shape object, rather than user input.

OK, it’s a bit of a contrived example, but it does answer the question “could I pass those methods to another method” — and this is the basis of things like Spring.

Note that some languages allow you to pass methods directly to other methods, without wrapping them in a class as we have here. This is called “functional programming”, and usually the “methods” are called “functions”.