How to detect a key press in Java

Question

My son (aged 11) who is learning Java is going to enter a question and some code. He tells me he has not been able to find the answer to this question on the site. You will

Answer 1

KeyListener

You should be putting his KeyListener Event within the class you need it not in the Main Method!

addKeyListener(new KeyListener() {
    public void keyPressed(KeyEvent e) {
        //This is where you want to implement your key!
        if(e.getKeyCode() == KeyEvent.VK_SPACE){
             //Fire Gun!
        }
        ....
    }

    public void keyReleased(KeyEvent e) { //I dont really use these!
    }

    public void keyTyped(KeyEvent e) { //I dont really use these!
    }
});

More on Keys here: KeyListeners

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Public and Private:

Now for Public and Private, there is already an answer on StackOVerflow which I think does the job pretty well! Here

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Functions/Methods and Void:

As for Void, It is used in functions where you wish to return nothing! I do not know how well you know about functions but let me give you an example:

int sum;
public int addReturn(int x, int y){
    sum = x +y;
    return sum;
}

What this does is it adds the two ints given as x and y and then returns the sum as an integer!

With void what you can do is:

int sum;
public void add(int x, int y){
    sum = x+ y;
}

Here you return nothing but it still stores x+y into sum!

So in your class:

int Summation, x = 10, y = 10;
summation = addReturn(x,y); //<-- This will place summation = 10+10 = 20

For the void function you do not need to make a variable since it doesnt return a value, rather it sets the value within the function. All you need to do is call it

add(x,y);

If you need more help just comment! :) Also I find it awesome that your son is so interested in Java at such a young age. Great Parenting :D