Assignment Operators

1. Introduction

Assignment operators in Java are used to assign values to variables.
The most commonly used assignment operator is =, but Java provides several compound assignment operators that simplify expressions and make code cleaner.

Assignment operators help you:

• Update variable values efficiently
• Reduce repetitive code
• Perform arithmetic and assignment in one step
• Improve readability in loops and calculations

This document explains each assignment operator with examples.

2. Basic Assignment Operator (=)

This operator assigns the value on the right-hand side (RHS) to the left-hand side (LHS) variable.

Syntax:

variable = value;

Example:

int x = 10;
String name = "John";

3. Compound Assignment Operators

Compound operators perform an operation and assignment in a single step.

Example:

x = x + 5;

Can be written as:

x += 5;

List of Compound Assignment Operators

4. Detailed Examples

4.1 Addition Assignment (+=)

int x = 10;
x += 5; 

Now:

x = 15

4.2 Subtraction Assignment (-=)

int x = 20;
x -= 4;

Now:

x = 16

4.3 Multiplication Assignment (*=)

int x = 7;
x *= 3;

Now:

x = 21

4.4 Division Assignment (/=)

int x = 40;
x /= 5;

Now:

x = 8

4.5 Modulus Assignment (%=)

int x = 13;
x %= 5;

Now:

x = 3

5. Bitwise Assignment Operators

These work at the bit level.

Example:

int x = 6;   // binary: 110
x &= 3;     // binary: 011

Now:

x = 2   // binary: 010

6. Shift Assignment Operators

Used to shift bits to the left or right.

Left shift:

int x = 4;   // 0100
x <<= 1;     // becomes 1000

Now:

x = 8

Right shift:

int x = 16; // 10000
x >>= 2;    // becomes 00010

Now:

x = 4

7. Real-World Use Cases

Loop counters

i += 2; // increment by 2

Summations

sum += value;

Reducing repetitive arithmetic

total -= discount;
balance *= rate;

Working with bitwise flags

permissions |= READ;
permissions &= ~WRITE;

8. Common Mistakes

• Using /= with integers (may cause integer division)
• Forgetting type limitations with += on small types (e.g., byte/short)
• Confusing x += y with x =+ y (which assigns positive value)

Bad:

x =+ 5; // means x = +5, not x += 5

9. Summary

• Assignment operators simplify updating variable values.
• = is the basic operator; others combine arithmetic and assignment.
• Compound operators help write cleaner and shorter code.
• Bitwise and shift assignment operators are useful for performance and low-level programming.
• Understanding assignment operators is essential for loops, conditions, and calculations.