Java Programming/Keywords/instanceof

is a keyword. It checks if an object reference is an instance of a type, and returns a boolean value; The <object-reference> will return true for all non-null object references, since all Java objects are inherited from . will always return if <object-reference> is . Syntax: <object-reference> TypeName For example: class Fruit { //... } class Apple extends Fruit { //... } class Orange extends Fruit { //... } public class Test { public static void main(String[] args) { Collection<Object> coll = new ArrayList<Object>(); Apple app1 = new Apple(); Apple app2 = new Apple(); coll.add(app1); coll.add(app2); Orange or1 = new Orange(); Orange or2 = new Orange(); coll.add(or1); coll.add(or2); printColl(coll); } private static String printColl( Collection<?> coll ) { for (Object obj : coll) { if ( obj instanceof Object ) { System.out.print("It is a Java Object and"); } if ( obj instanceof Fruit ) { System.out.print("It is a Fruit and"); } if ( obj instanceof Apple ) { System.out.println("it is an Apple"); } if ( obj instanceof Orange ) { System.out.println("it is an Orange"); } } } } Run the program: java Test The output: It is a Java Object and It is a Fruit and it is an Apple It is a Java Object and It is a Fruit and it is an Apple It is a Java Object and It is a Fruit and it is an Orange It is a Java Object and It is a Fruit and it is an Orange Note that the operator can also be applied to interfaces. For example, if the example above was enhanced with the interface interface Edible { //... } and the classes modified such that they implemented this interface class Orange extends Fruit implements Edible { ... } we could ask if our object were edible. if ( obj instanceof Edible ) { System.out.println("it is edible"); } deep