Zero2OneDev - Master Programming from Zero to One

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What are Operators?

Operators are symbols that perform operations on variables and values. Java has multiple types of operators for different operations.

Arithmetic Operators

Used for mathematical calculations:

+ (Addition), - (Subtraction), * (Multiplication)
/ (Division), % (Modulus - remainder)

Relational Operators

Used to compare values. Return boolean (true/false):

== (Equal), != (Not equal)
< (Less), > (Greater)
<= (Less or equal), >= (Greater or equal)

Logical Operators

Used for boolean operations:

&& (AND - both must be true), || (OR - either can be true)
! (NOT - reverses boolean value)

Assignment Operators

Used to assign values:

= (Assign), +=, -=, *=, /=

Increment/Decrement Operators

++ (Increment), -- (Decrement)
Pre-increment: ++x, Post-increment: x++

⚠️ Gotcha: ++x increments BEFORE returning, while x++ increments AFTER returning. This matters when used in expressions!

Code Examples

Arithmetic operators in action

java

1// Arithmetic operators
2int a = 10, b = 3;
3System.out.println(a + b);      // 13
4System.out.println(a - b);      // 7
5System.out.println(a * b);      // 30
6System.out.println(a / b);      // 3
7System.out.println(a % b);      // 1

Comparison operators return boolean values

java

1// Relational operators
2int x = 10, y = 20;
3System.out.println(x == y);     // false
4System.out.println(x != y);     // true
5System.out.println(x < y);      // true
6System.out.println(x > y);      // false
7System.out.println(x <= y);     // true
8System.out.println(x >= y);     // false

Logical operators for combining boolean conditions

java

1// Logical operators
2boolean p = true, q = false;
3System.out.println(p && q);     // false (AND)
4System.out.println(p || q);     // true (OR)
5System.out.println(!p);         // false (NOT)
6
7// Practical use
8int age = 25;
9boolean isStudent = true;
10if (age >= 18 && isStudent) {
11    System.out.println("Student over 18");
12}

The important difference between ++x and x++

java

1// Pre vs Post increment
2int x = 5;
3int y = ++x;  // Pre-increment: x becomes 6, then y = 6
4System.out.println(x + ", " + y); // 6, 6
5
6int a = 5;
7int b = a++;  // Post-increment: b = 5, then a becomes 6
8System.out.println(a + ", " + b); // 6, 5

Use Cases

Mathematical calculations and data manipulation
Comparing values in conditional statements
Combining multiple conditions with logical operators
Updating variables with compound assignment operators
Incrementing loop counters
Building complex boolean expressions

Common Mistakes to Avoid

Using = (assignment) instead of == (comparison)
Confusing && (AND) with || (OR)
Not understanding operator precedence
Pre vs post increment behavior differences
Integer division truncating results (10/3 = 3, not 3.33)
Comparing objects with == instead of .equals()