Equality, Relational, and Conditional Operators in Java

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In this chapter, we will learn about Equality, Relational, and Conditional Operators in Java programming language with examples.

1. The Equality and Relational Operators

The equality and relational operators determine if one operand is greater than, less than, equal to, or not equal to another operand. The majority of these operators will probably look familiar to you as well. Keep in mind that you must use "==", not "=", when testing if two primitive values are equal.

The following program, ComparisonDemo, tests the comparison operators:

class ComparisonDemo {

    public static void main(String[] args) {
        int value1 = 1;
        int value2 = 2;
        if (value1 == value2)
            System.out.println("value1 == value2");
        if (value1 != value2)
            System.out.println("value1 != value2");
        if (value1 > value2)
            System.out.println("value1 > value2");
        if (value1 < value2)
            System.out.println("value1 < value2");
        if (value1 <= value2)
            System.out.println("value1 <= value2");
    }
}

Output:

value1 != value2
value1 <  value2
value1 <= value2

2. The Conditional Operators

The && and || operators perform Conditional-AND and Conditional-OR operations on two boolean expressions. These operators exhibit "short-circuiting" behavior, which means that the second operand is evaluated only if needed.

&& Conditional-AND
|| Conditional-OR

Example:

class ConditionalDemo1 {

    public static void main(String[] args) {
        int value1 = 1;
        int value2 = 2;
        if ((value1 == 1) && (value2 == 2))
            System.out.println("value1 is 1 AND value2 is 2");
        if ((value1 == 1) || (value2 == 1))
            System.out.println("value1 is 1 OR value2 is 1");
    }
}

3. Ternary Operator

Java includes a special ternary (three-way) operator that can replace certain types of if-then-else statements.

Syntax:

expression1 ? expression2 : expression3

Here, expression1 can be any expression that evaluates to a boolean value. If expression1 is true, then expression2 is evaluated; otherwise, expression3 is evaluated.

Here is a program that demonstrates the ternary operator. It uses it to obtain the absolute value of a variable.

package net.javaguides.corejava.operators.ternary;

public class Ternary {
    public static void main(String args[]) {
        int i, k;
        i = 10;
        k = i < 0 ? -i : i; // get absolute value of i
        System.out.print("Absolute value of ");
        System.out.println(i + " is " + k);
        i = -10;
        k = i < 0 ? -i : i; // get absolute value of i
        System.out.print("Absolute value of ");
        System.out.println(i + " is " + k);
    }
}

Output:

Absolute value of 10 is 10
Absolute value of -10 is 10

4. The Type Comparison Operator instanceof

The instanceof operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.

The following program, InstanceofDemo, defines a parent class (named Parent), a simple interface (named MyInterface), and a child class (named Child) that inherits from the parent and implements the interface.

class InstanceofDemo {
    public static void main(String[] args) {

        Parent obj1 = new Parent();
        Parent obj2 = new Child();

        System.out.println("obj1 instanceof Parent: " +
            (obj1 instanceof Parent));
        System.out.println("obj1 instanceof Child: " +
            (obj1 instanceof Child));
        System.out.println("obj1 instanceof MyInterface: " +
            (obj1 instanceof MyInterface));
        System.out.println("obj2 instanceof Parent: " +
            (obj2 instanceof Parent));
        System.out.println("obj2 instanceof Child: " +
            (obj2 instanceof Child));
        System.out.println("obj2 instanceof MyInterface: " +
            (obj2 instanceof MyInterface));
    }
}

class Parent {}
class Child extends Parent implements MyInterface {}
interface MyInterface {}

Output:

obj1 instanceof Parent: true
obj1 instanceof Child: false
obj1 instanceof MyInterface: false
obj2 instanceof Parent: true
obj2 instanceof Child: true
obj2 instanceof MyInterface: true

When using the instanceof operator, keep in mind that null is not an instance of anything.

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