Java instanceof keyword example

In Java, the instanceof keyword is used to check whether an object is an instance of a particular class or interface. For example:

Object msg = new String("Hello");
if (msg instanceof String) {
    System.out.println("A String");
}

The instanceof statement returns true if the variable is of type (or subtype) of the specified class. The above code will give the output "A String" because msg is of type String.

So we can consider instanceof as an operator. It is widely used in when overriding the equals() method, for example:

public class Student {
 
    public boolean equals(Object obj) {
        if (obj instanceof Student) {
        	// comparing...
        }
 
        return false;
    }
}

Related keyword: if..else. See all keywords in Java.

Other Recommended Tutorials:

• 9 Rules about Constructors in Java
• 12 Rules and Examples About Inheritance in Java
• 12 Rules of Overriding in Java You Should Know
• 10 Java Core Best Practices Every Java Programmer Should Know
• Understand Interfaces in Java
• Understand how variables are passed in Java
• Understand encapsulation in Java

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He started programming with Java in the time of Java 1.4 and has been falling in love with Java since then. Make friend with him on Facebook and watch his Java videos you YouTube.