Question

I am having a problem where, after performing a simple mathematical operation on the elements of an array, I return this array and receive only what was changed in the specific function.

You may be thinking, “Great. That’s what’s supposed to happen.” You are correct, but let me give another situation: I call functionA below, then I call functionB. Instead of getting 1 1 1 as the output, I get 0 3 -2, the exact same as functionB without the call to functionA.

Here’s the example’s code:

public static int[] position = new int[3];  //This array is filled 
                                            //with [0,0,0] using a for-loop

    public static int[] functionA(int[] position){

        position[0] =+ 1;  //=+ operator use
        position[1] =- 2;  //=- operator use
        position[2] =+ 3;

        return position;
    }

    public static int[] functionB(int[] position){

        position[0] =+ 0;
        position[1] =+ 3;
        position[2] =- 2;

        return position;
    }

    functionA(position);
    functionB(position);

    System.out.println(myPosition[0]);  //0
    System.out.println(myPosition[1]);  //1
    System.out.println(myPosition[2]);  //-2

I do not understand where I went wrong. Am I using the =+ or =- operators incorrectly or am I returning the array incorrectly, or is there something I am totally missing?

Any help is appreciated.

Answer 1

Use += instead of =+, and -= instead of =-.

Take a look on this SO question: What is the difference between a += b and a =+ b , also a++ and ++a?