Java Ternary Operator

In this unit, we will learn about Ternary Operator which is a one-liner replacement for if...else statements.

1. Ternary Operator

Ternary Operator is a conditional operator which works similar to if...else statements. When compared to if...else statements, the ternary operator consists of a shorter syntax.

Syntax

condition ? expression1 : expression2;

The ternary operator takes three operands (i.e, condition, expression1, and expression2). Here, the condition is evaluated and,

  • If the condition is true, expression1 is executed and the result is returned.

  • If the condition is false, expression2 is executed and the result is returned.

 

Example 1:

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int token = input.nextInt();

        String message = (token == 20) ? "Collect Water Bottle" : "Invalid Token" ;

        System.out.println(message);

        input.close();

    }

}

 

Here,

  • token == 20 is the condition.

  • "Collect Water Bottle" is expression1.

  • "Invalid Token" is expression2.

Let's understand the working of the ternary operator with different inputs.

Input & Output 1

Input & Output 2

 

Example 2:

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int num1 = input.nextInt();

        int num2 = input.nextInt();

        int largest = num1 > num2 ? num1 : num2 ;

 

        System.out.println(largest);

        input.close();

    }

}

 

Input

345 689

Output

689

 

The above code prints the largest number between two given numbers. It isn't possible to replace every if...else statement with a ternary operator, but in some cases, it is a great tool to make our code more readable and shorter.

 

2. Nested Ternary Operator

A Ternary operator can be used inside another ternary operator. It is called the nested ternary operator.

Example

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int a = input.nextInt();

        int b = input.nextInt();

        int c = input.nextInt();

        int largest = (a >= b) ? ((a >= c) ? a : c) : ((b >= c) ? b : c);

 

        System.out.println(largest + " is the largest among "+ a + ", " + b + ", and " + c);

        input.close();

    }

}

 

In the outer ternary operator,

  • (a >= b) is the condition.

  • ((a >= c) ? a : c) is the expression1.

  • ((b >= c) ? b : c) is the expression2.

The code aims to find the largest number among the given three numbers.

Input & Output 1

Input & Output 2

 

Possible Mistakes

Mistake 1: Return statements in expressions

In the ternary operator, putting return statements in the expressions is illegal. It always returns the result of the expression.

Wrong  Code

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int num = input.nextInt();

        boolean isDivisibleByFive = (num % 5 == 0) ? return true : return false;

 

        System.out.println(isDivisibleByFive);

        input.close();

    }

}

 

Input

55

Output

file.java:7: error: illegal start of expression

      boolean isDivisibleByFive = (num % 5 == 0) ? return true : return false;

                                       ^

file.java:7: error: ';' expected

      boolean isDivisibleByFive = (num % 5 == 0) ? return true : return false;

                                                ^

2 errors

 

Correct Code

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int num = input.nextInt();

        boolean isDivisibleByFive = (num % 5 == 0) ? true : false;

 

        System.out.println(isDivisibleByFive);

        input.close();

    }

}

 

Input

55

Output

true

Mistake 2: Replacing colon (:) with a semicolon (;)

 

Error Code

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int num = input.nextInt();

        boolean isDivisibleByFive = (num % 5 == 0) ? true ; false;

 

        System.out.println(isDivisibleByFive);

        input.close();

    }

}

 

Input

245

Output

file.java:7: error: : expected

      boolean isDivisibleByFive = (num % 5 == 0) ? true ; false;

                                          ^

file.java:7: error: illegal start of expression

      boolean isDivisibleByFive = (num % 5 == 0) ? true ; false;

                                           ^

file.java:7: error: not a statement

      boolean isDivisibleByFive = (num % 5 == 0) ? true ; false;

                                             ^

3 errors

 

Working Code

import java.util.Scanner;

class Main {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int num = input.nextInt();

        boolean isDivisibleByFive = (num % 5 == 0) ? true : false;

 

        System.out.println(isDivisibleByFive);

        input.close();

    }

}

 

Input

245

Output

true

 

Summary

  • Ternary Operator is a one-liner replacement for if...else statements. It takes three operands (i.e, condition, expression1, and expression2).

  • The ternary operator evaluates the condition and executes a block of code based on the result of the condition.

  • A Ternary operator can be used inside another ternary operator. It is called the nested ternary operator.

  • The ternary operator always returns the value of the expression which is executed

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