instanceof and getClass()

instanceof tests whether the object reference on the left-hand side (LHS) is an instance of the type on the right-hand side (RHS) or some subtype.

getClass() == … tests whether the types are identical.

public class MainClass {
public static void main(String[] a) {
String s = "Hello";
if (s instanceof java.lang.String) {
System.out.println("is a String");
}
}
}

is a String

However, applying instanceof on a null reference variable returns false. For example, the following if statement returns false.

public class MainClass {
public static void main(String[] a) {

String s = null;
if (s instanceof java.lang.String) {
System.out.println("true");
} else {
System.out.println("false");
}
}

}

false

Since a subclass ‘is a’ type of its superclass, the following if statement, where Child is a subclass of Parent, returns true.

class Parent {
public Parent() {

}
}

class Child extends Parent {
public Child() {
super();
}
}

public class MainClass {
public static void main(String[] a) {

Child child = new Child();
if (child instanceof Parent) {
System.out.println("true");
}

}

}

true