Returning Arrays

Many of the methods we have written have the return type of void.

• This means they don't return anything.

public static void allSing(PopStar[] stars) {
  //...
}

Other methods return data. * The type of the data is the return type for the method.

This method returns a String. * It must return a String (or null).

public static String addExclamations(String s) {
  String sExc = s + "!!!";
  return sExc;
}

We can call the method and assign the returned data to a variable.

String output = addExclamations("Yo"); // output = Yo!!!

Returning Array References

Using the same process, we can return arrays references from our methods.

This method creates a String[] and returns a reference to the array.

public static String[] createList() {
  String stringArr[] = {"Danny", "Donnie", "Joey", "Jon", "Jordan"};
  return stringArr;
}

Again, we call the method and assign the returned reference to a variable.

String[] list = createList();

Practice Exercise

We can always tell what a method returns by looking at the return type. This is just what the Java compiler does to see if our method calls are legal.

The array is created inside a method, so why hasn't the array gone out of scope when the method ends?

• Inside the method, the array object is instantiated with the call to new. This makes it exist outside the method.
• The reference variable stringArr is like the address on a house.
• When we return the stringArr, we're returning a copy of the address.
• The calling method gets that address, so it knows where the array lives.

1. Java instantiates the array object.
2. createList returns the reference to the array.
3. Array reference is stored in a variable outside createList scope.

Drill

AdvancedArrays/com.example.advancedarrays.drills.ReturningArrays * Add a method called public static PopStar[] createBand(). * Move the code that creates and fills a PopStar array into this method. Be sure to return the array from the method (since it's return type is PopStar[]). * Call the method from main and store the array reference in a variable. * Pass the array to the allSing method. * Run the program.

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