Accepting and Returning Arrays in Java

This section explains the code listed in the previous section.  The following is the new “method” I introduced in the class “MyCalc”:

    public int[] getDoubledValues() {
        int[] b = new int[a.length];
        for(int i=0;i<a.length;i++) {
            b[i] = a[i] + a[i];
        }
        return b;
    }

Let us consider the first line:

    public int[] getDoubledValues() {

From the above line, we know the name of the method is “getDoubledValues,” it accepts no parameters and returns an array of type “int.”  You must observe the square brackets near the keyword “int.”  That means the method is trying to return an array of type “int” back to the calling program.  We have the second line as follows:

        int[] b = new int[a.length];

In the above statement, we are simply creating a new temporary integer array named “b.”  The size of the "b" array must be the same as that of “a.”  And thus I used “a.length” to get the size of array “a.”  Further proceeding we have the following:

        for(int i=0;i<a.length;i++) {
            b[i] = a[i] + a[i];
        }

The above loop simply iterates through all the elements available in “a,” doubles those elements and places them in “b.”  Finally, we return back to the "b" array with the following statement:

        return b;

Now, if we proceed to our “test” frame, we have the following initially:

        MyCalc obj1 = new MyCalc();
        MyCalc obj2 = new MyCalc();
        int[] ar = {12,23,34,45,56,67};
        obj1.setValues(ar);
        obj2.setValues(obj1.getDoubledValues());

I declared two objects named “obj1” and “obj2.”  Now, both of them internally contain the same members (a, setValues, getDoubledValues, getSum).  You can also observe that I am simply passing an array of values (available in “ar”) to only “obj1.”  The most crucial part is the following statement:

        obj2.setValues(obj1.getDoubledValues());

It is a bit difficult to understand the above statement (for beginners). The above statement first calls the method “getDoubledValues” from the object “obj1.”  The “getDoubledValues” returns an array, which is further passed to the method “setValues” from “obj2.”  To eliminate the confusion, we can even declare our own temporary array and assign “getDoubledValues” to it, and finally pass the same to “setValues.” 

        int r;
        r = obj1.getSum();
        this.lblMsg.setText("Sum = " + String.valueOf(r));
        r = obj2.getSum();
        this.lblMsg2.setText("Sum = " + String.valueOf(r));

The above code does nothing but get the sum of all elements in array “a” and display the same.  My previous article gives you a better understanding of this.