Android Development with Kotlin

Collection variance

In Java, arrays are co-variant. By default, we can pass an array of String[] even if an array of Object[] is expected:

    public class Computer {        public Computer() {            String[] stringArray = new String[]{"a", "b", "c"};            printArray(stringArray); //Pass instance of String[]        }        void printArray(Object[] array) {             //Define parameter of type Object[]            System.out.print(array);        }    }

This behavior was important in early versions of Java, because it allowed us to use different types of array as arguments:

    // Java    static void print(Object[] array) {        for (int i = 0; i <= array.length - 1; i++)        System.out.print(array[i] + " ");        System.out.println();    }    // Usage    String[] fruits = new String[] {"Pineapple","Apple", "Orange",                                     "Banana"}; print(fruits); ...