Operators in Java

# CHAPTER 5

Operators in Java #

1. Introduction #

2. Learning Objectives #

• Use arithmetic operators for calculations.

• Compare values with relational operators.

• Combine conditions with logical operators.

• Understand assignment and compound assignment operators.

• Use bitwise and ternary operators.

3. Arithmetic Operators #

int a = 17, b = 5;
System.out.println("Addition: " + (a + b));       // 22
System.out.println("Subtraction: " + (a - b));    // 12
System.out.println("Multiplication: " + (a * b)); // 85
System.out.println("Division: " + (a / b));       // 3 (not 3.4!)
System.out.println("Modulus: " + (a % b));        // 2

Important: Integer division truncates the decimal! Use double for accurate division:

double result = 17.0 / 5;  // 3.4

4. Increment and Decrement Operators #

int x = 5;
System.out.println(x++); // Prints 5 (post-increment: use THEN increment)
System.out.println(x);   // Prints 6

int y = 5;
System.out.println(++y); // Prints 6 (pre-increment: increment THEN use)

5. Relational (Comparison) Operators #

int age = 20;
System.out.println(age >= 18);  // true (can vote)
System.out.println(age == 21);  // false

6. Logical Operators #

int age = 25;
boolean hasLicense = true;

// AND: both conditions must be true
if (age >= 18 && hasLicense) {
    System.out.println("You can drive!");
}

// OR: at least one must be true
if (age < 13 || age > 65) {
    System.out.println("Discount ticket!");
}

// NOT: reverses the result
boolean isRaining = false;
if (!isRaining) {
    System.out.println("Go for a walk!");
}

7. Assignment Operators #

int score = 100;
score += 10;  // score is now 110
score -= 5;   // score is now 105
score *= 2;   // score is now 210

8. Ternary Operator #

Syntax: condition ? valueIfTrue : valueIfFalse

int age = 20;
String status = (age >= 18) ? "Adult" : "Minor";
System.out.println(status); // "Adult"

int a = 10, b = 20;
int max = (a > b) ? a : b;
System.out.println("Max: " + max); // 20

9. Bitwise Operators (Advanced Beginner) #

int a = 5;  // Binary: 0101
int b = 3;  // Binary: 0011

System.out.println(a & b);  // 1  (0001)
System.out.println(a | b);  // 7  (0111)
System.out.println(a ^ b);  // 6  (0110)

10. Operator Precedence #

1. 1. () — Parentheses

1. 2. ++, -- — Increment/Decrement

1. 3. *, /, % — Multiplication, Division, Modulus

1. 4. +, - — Addition, Subtraction

1. 5. <, >, <=, >= — Relational

1. 6. ==, != — Equality

1. 7. && — Logical AND

1. 8. || — Logical OR

1. 9. =, +=, -= — Assignment

Tip: When in doubt, use parentheses to make your intent clear!

11. Common Mistakes #

• Using = instead of ==: if (x = 5) is assignment, not comparison.

• Integer division surprise: 5 / 2 returns 2, not 2.5.

• Post vs Pre increment confusion: x++ and ++x behave differently when used in expressions.

12. Best Practices #

• Always use parentheses for complex expressions to improve readability.

• Use compound operators (+=, -=) for cleaner code.

• Use the ternary operator for simple conditional assignments only.

13. Exercises #

1. 1. Write a program that calculates the area and perimeter of a rectangle.

1. 2. Write a program that swaps two numbers without using a third variable (hint: use XOR).

1. 3. Write a program using the ternary operator to check if a number is even or odd.

14. MCQ Quiz with Answers #

15. Interview Questions #

• Q: What is the difference between ++i and i++?

• Q: What is short-circuit evaluation in && and ||?

• Q: How does integer division work in Java?

• Q: Can the ternary operator be nested? Should it be?

16. Summary #

17. Next Chapter Recommendation #