import java.util.Arrays; public class Demo2 { public static void main(String[] args) { Circle[] arr = new Circle[4]; arr[0] = new Circle("red", 4); arr[1] = new Circle("green", 3); arr[2] = new Circle("blue", 5); arr[3] = new Circle("yellow", 2); for ( int i = 0; i < arr.length; i++ ) System.out.print( arr[i] + " , "); System.out.println(); Arrays.sort( arr ); // Uses upcasting ! for ( int i = 0; i < arr.length; i++ ) System.out.print( arr[i] + " , "); System.out.println(); } }