Relational operators in Java

Introduction

Relational operators help us compare two values to see how they relate to each other, like if one is bigger or smaller.

Checking if a student's score is above the passing mark.

Deciding if a person is old enough to vote.

Comparing prices to find the cheaper product.

Determining if a number is equal to another number.

Finding out if a temperature is below freezing.

Syntax

Java

value1 < value2
value1 <= value2
value1 > value2
value1 >= value2
value1 == value2
value1 != value2

Use == to check if two values are equal.

Use != to check if two values are not equal.

Examples

This checks if a is less than b. The result will be true.

Java

int a = 5;
int b = 10;
boolean result = a < b;

This checks if age is at least 18 to allow voting.

Java

int age = 18;
boolean canVote = age >= 18;

This checks if x and y are equal.

Java

int x = 7;
int y = 7;
boolean equal = x == y;

This checks if temp is not zero (not freezing).

Java

int temp = 30;
boolean notFreezing = temp != 0;

Sample Program

This program compares the student's score with the passing score using relational operators and prints the results.

Java

public class RelationalOperatorsDemo {
    public static void main(String[] args) {
        int score = 75;
        int passingScore = 60;

        System.out.println("Score: " + score);
        System.out.println("Passing Score: " + passingScore);

        System.out.println("Did the student pass? " + (score >= passingScore));
        System.out.println("Is the score less than 50? " + (score < 50));
        System.out.println("Is the score equal to 75? " + (score == 75));
        System.out.println("Is the score not equal to 100? " + (score != 100));
    }
}

Important Notes

Relational operators always return a boolean value: true or false.

Use parentheses to make complex comparisons clear.

Summary

Relational operators compare two values and return true or false.

They include <, <=, >, >=, ==, and !=.

They are useful for making decisions in programs.

Practice

1. Which of the following relational operators in Java checks if two values are not equal?

easy

A. ==

B. >=

C. !=

D. <

Solution

1. Step 1: Understand the meaning of relational operators

   Relational operators compare two values and return true or false based on the comparison.

2. Step 2: Identify the operator for 'not equal'

   The operator '!=' means 'not equal to' in Java.

3. Final Answer:

   != -> Option C

4. Quick Check:

   Not equal operator = != [OK]

Hint: Remember: '!=' means not equal in Java [OK]

Common Mistakes:

• Confusing '!=' with '=='
• Using '=' instead of '=='
• Mixing up '<' and '<='

2. Which of the following is the correct syntax to check if variable a is greater than or equal to variable b in Java?

easy

A. a => b

B. a >= b

C. a =< b

D. a =>= b

Solution

1. Step 1: Recall the correct relational operator syntax

   The operator for 'greater than or equal to' is written as '>=' in Java.

2. Step 2: Check each option for correct syntax

   a >= b uses '>=', which is correct. Other options have invalid syntax.

3. Final Answer:

   a >= b -> Option B

4. Quick Check:

   Greater or equal operator = >= [OK]

Hint: Use '>=' for greater or equal, not '=>' or '=<' [OK]

Common Mistakes:

• Writing '=>' instead of '>='
• Using '=' instead of '=='
• Confusing '<=' and '=>'

3. What will be the output of the following Java code?

int x = 5;
int y = 10;
System.out.println(x < y);
System.out.println(x == y);
System.out.println(x != y);

medium

A. false false true

B. false true false

C. true true false

D. true false true

Solution

1. Step 1: Evaluate each relational expression

   x is 5 and y is 10. So, x < y is true, x == y is false, and x != y is true.

2. Step 2: Write the output in order

   The printed output will be: true false true.

3. Final Answer:

   true false true -> Option D

4. Quick Check:

   5 < 10 = true, 5 == 10 = false, 5 != 10 = true [OK]

Hint: Compare values step-by-step to get true/false results [OK]

Common Mistakes:

• Mixing up == and !=
• Assuming x == y is true
• Confusing output order

4. Identify the error in the following Java code snippet:

int a = 7;
int b = 3;
if (a <> b) {
    System.out.println("Not equal");
}

medium

A. The operator '<>' is invalid in Java

B. Missing semicolon after if statement

C. Variables a and b are not declared

D. The print statement syntax is incorrect

Solution

1. Step 1: Check the relational operator used

   The operator '<>' is not a valid relational operator in Java. Java uses '!=' for not equal.

2. Step 2: Verify other syntax elements

   Semicolons and print statement are correct. Variables are declared properly.

3. Final Answer:

   The operator '<>' is invalid in Java -> Option A

4. Quick Check:

   Use '!=' for not equal, not '<>' [OK]

Hint: Use '!=' for not equal; '<>' is invalid in Java [OK]

Common Mistakes:

• Using '<>' instead of '!='
• Forgetting semicolons
• Incorrect print syntax

5. Given the code below, what will be the output?

int a = 4;
int b = 4;
int c = 5;
boolean result = (a <= b) && (c > b);
System.out.println(result);

Choose the correct output.

hard

A. true

B. false

C. Compilation error

D. Runtime exception

Solution

1. Step 1: Evaluate each relational expression

   a <= b is 4 <= 4, which is true. c > b is 5 > 4, which is true.

2. Step 2: Evaluate the logical AND operation

   Both conditions are true, so (true && true) is true.

3. Final Answer:

   true -> Option A

4. Quick Check:

   4 <= 4 and 5 > 4 = true [OK]

Hint: Both conditions must be true for && to be true [OK]

Common Mistakes:

• Confusing && with ||
• Misreading <= as < only
• Assuming false if equal values