Relational Operators

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1. Introduction

Relational operators in Java are used to compare two values.
They always return a boolean result (true or false).

These operators are essential for:

• Decision-making (if, else)
• Loop conditions
• Validations
• Sorting and comparison logic
• Implementing business rules

Understanding relational operators is fundamental to writing correct conditional logic in Java.

2. List of Relational Operators

Java provides six relational operators:

All relational operators return a boolean value.

3. Relational Operators Explained

3.1 Equal To (==)

Checks if two values are equal.

int a = 10, b = 10;
System.out.println(a == b); // true

For objects, == compares references, not values.

Example:

String s1 = new String("Hi");
String s2 = new String("Hi");
System.out.println(s1 == s2); // false (different memory locations)

3.2 Not Equal To (!=)

Returns true if values are not equal.

int a = 10, b = 20;
System.out.println(a != b); // true

For objects, also compares references:

String s1 = "Hello";
String s2 = "World";
System.out.println(s1 != s2); // true

3.3 Greater Than (>)

int a = 15, b = 10;
System.out.println(a > b); // true

3.4 Less Than (<)

int a = 5, b = 12;
System.out.println(a < b); // true

3.5 Greater Than or Equal To (>=)

int marks = 75;
System.out.println(marks >= 60); // true (passing marks)

3.6 Less Than or Equal To (<=)

int age = 18;
System.out.println(age <= 18); // true

4. Relational Operators with Different Data Types

Java allows relational operations on:

• Numeric types (int, double, float, etc.)
• Characters (char)
• Booleans → NOT allowed, except comparison using == and !=
• Objects → only == and != allowed (reference comparison)

4.1 Character Comparison

char c1 = 'A';  // ASCII 65
char c2 = 'B';  // ASCII 66
System.out.println(c1 < c2); // true

Java compares the Unicode values of characters.

4.2 Numeric Comparisons

Mixing numeric types:

int a = 10;
double b = 10.0;
System.out.println(a == b); // true (numeric promotion)

5. Relational Operators in Real Conditions

Example 1: Age Check

if (age >= 18) {
    System.out.println("Eligible to vote");
}

Example 2: Password Length Validation

if (password.length() < 8) {
    System.out.println("Password too short");
}

Example 3: Comparing Scores

if (score > highScore) {
    System.out.println("New high score!");
}

6. Object Comparison – Important Note

Using relational operators (>, <, >=, <=) on objects like String, Integer, or custom classes is not allowed in Java.

Example (INVALID):

String s1 = "Apple";
String s2 = "Banana";

// if (s1 > s2) {}  // ERROR

For object value comparison, use:

s1.equals(s2);

Or for sorting comparisons:

s1.compareTo(s2);

7. Common Mistakes to Avoid

• Using == to compare strings — use .equals()
• Expecting relational operators to work on objects
• Confusing = (assignment) with == (comparison)
• Assuming floating-point comparisons are always accurate (precision issues with double)

Example:

double x = 0.1 + 0.2;
System.out.println(x == 0.3); // false (precision issue)

8. Summary

• Relational operators compare two values and return boolean results.
• They are used extensively in branching and looping conditions.
• Work on numbers, characters, and references (with limitations).
• For object value comparison, always use .equals() or .compareTo().