instanceof Java is a binary operator (operator), is also a Java reserved keywords. Its role is to judge whether the object for the left and the right instance of the class, returns boolean values. It is used to determine whether an object is an instance of class Class.
usage:
boolean result = object instanceof class
parameter:
result: boolean type.
object: Required. Any object expression.
class: Required. Any object class defined.
Description:
If the object is an instance of the class, then returns true. If the object is not an instance of the class or object is null, false is returned.
example:
package com.instanceoftest;
interface A { }
class B implements A {} // B to A is achieved
class C extends B {} // C B Inherited
class D { }
class instanceoftest {
public static void main(String[] args) {
A a = null;
B b = null;
boolean res;
System.out.println("instanceoftest test case 1: ------------------");
res = a instanceof A;
System.out.println("a instanceof A: " + res); // a instanceof A:false
res = b instanceof B;
System.out.println("b instanceof B: " + res); // b instanceof B: false
res = b instanceof B;
System.out.println("b instanceof B: " + res); // b instanceof B: false
System.out.println("\ninstanceoftest test case 2: ------------------");
a = new B();
b = new B();
res = a instanceof A;
System.out.println("a instanceof A: " + res); // a instanceof A:true
res = a instanceof B;
System.out.println("a instanceof B: " + res); // a instanceof B:true
res = b instanceof A;
System.out.println("b instanceof A: " + res); // b instanceof A:true
res = b instanceof B;
System.out.println("b instanceof B: " + res); // b instanceof B:true
System.out.println("\ninstanceoftest test case 3: ------------------");
B b2 = new C();
res = b2 instanceof A;
System.out.println("b2 instanceof A: " + res); // b2 instanceof A:true
res = b2 instanceof B;
System.out.println("b2 instanceof B: " + res); // b2 instanceof A:true
res = b2 instanceof C;
System.out.println("b2 instanceof C: " + res); // b2 instanceof A:true
System.out.println("\ninstanceoftest test case 4: ------------------");
D d = new D();
res = d instanceof A;
System.out.println("d instanceof A: " + res); // d instanceof A:false
res = d instanceof B;
System.out.println("d instanceof B: " + res); // d instanceof B:false
res = d instanceof C;
System.out.println("d instanceof C: " + res); // d instanceof C:false
res = d instanceof D;
System.out.println("d instanceof D: " + res); // d instanceof D:true
}
}
}