Comparison Operators

Compare values in Java using ==, !=, >, <, >=, and <= - operators that return a boolean result.

Overview

Comparison operators compare two values and return a boolean result (true or false). They are the foundation of all decision-making in programs - every if statement, loop condition, and ternary expression uses them. Java has six comparison operators. They work naturally on primitive types. For objects (including Strings), == compares references (memory addresses), not content - use .equals() for content comparison.

Key Points

•== equal to (do not confuse with = assignment)
•!= not equal to
•> greater than, < less than
•>= greater than or equal to, <= less than or equal to
•All comparison operators return boolean: true or false
•For objects use .equals() - == on objects checks if they are the same object in memory, not equal content

Examples

All six comparison operators

public class Main {
    public static void main(String[] args) {
        int a = 10, b = 20;

        System.out.println(a == b);  // false
        System.out.println(a != b);  // true
        System.out.println(a > b);   // false
        System.out.println(a < b);   // true
        System.out.println(a >= 10); // true  (equal counts)
        System.out.println(b <= 15); // false
    }
}

The result is always true or false. These results are often used directly in if conditions.

Comparing in conditions

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

        if (score >= 90) {
            System.out.println("Grade: A");
        } else if (score >= 70) {
            System.out.println("Grade: B");
        } else {
            System.out.println("Grade: C or below");
        }

        int age = 17;
        System.out.println("Can vote: " + (age >= 18)); // false
    }
}

You can print a comparison result directly: System.out.println(age >= 18) prints false.

== on primitives vs objects

public class Main {
    public static void main(String[] args) {
        // Primitives: == compares values
        int x = 5, y = 5;
        System.out.println(x == y); // true ✓

        // Strings: == compares references (memory address)
        String s1 = new String("hello");
        String s2 = new String("hello");
        System.out.println(s1 == s2);      // false ✗ (different objects)
        System.out.println(s1.equals(s2)); // true  ✓ (same content)

        // String literals may be the same object (string pool)
        String a = "hi";
        String b = "hi";
        System.out.println(a == b); // true (but don't rely on this!)
    }
}

Always use .equals() for String (and object) comparison to avoid subtle bugs.

Common Mistakes

Writing = (assignment) instead of == (comparison) inside an if condition - Java will give a compile error for non-boolean assignment in if
Using == to compare Strings - this compares object references, not content; use .equals()
Confusing >= with => (there is no => comparison in Java; => is only for lambda expressions)

Note

Store comparison results in a boolean variable for clarity: `boolean isAdult = age >= 18;`. This makes later code that uses the result more readable.

Comparison Operators

Overview

Key Points

Examples

Common Mistakes

Note

Exercises

Knowledge Check

What does the expression `10 != 10` evaluate to?