Operators in Java

What are operators

Operators are symbols that do things with values — add them, compare them, or combine conditions. They are the basic building blocks of every calculation and decision in a program. Java groups them into arithmetic, assignment, comparison, logical, and increment/decrement.

Arithmetic operators

int a = 10, b = 3;
System.out.println(a + b);   // 13
System.out.println(a - b);   // 7
System.out.println(a * b);   // 30
System.out.println(a / b);   // 3  (integer division)
System.out.println(a % b);   // 1  (remainder)

Note a / b with two ints gives 3, not 3.33 — integer division drops the decimal. % gives the remainder, great for even/odd checks.

Assignment operators

int x = 10;
x += 5;   // x = x + 5  -> 15
x -= 3;   // x = x - 3  -> 12
x *= 2;   // x = x * 2  -> 24
System.out.println(x);

= assigns a value. Shortcuts like += and *= update a variable using its own current value, saving typing.

Comparison operators

int a = 10, b = 3;
System.out.println(a == b);   // false
System.out.println(a != b);   // true
System.out.println(a > b);    // true
System.out.println(a <= b);   // false

These compare two values and give a boolean (true/false). Remember == compares, while a single = assigns.

Logical operators

int age = 20;
boolean ok = (age > 18) && (age < 60);   // AND
boolean any = (age < 12) || (age > 18);  // OR
System.out.println(ok);
System.out.println(!ok);                 // NOT

&& (AND) is true only if both sides are true. || (OR) is true if either side is. ! (NOT) flips true and false.

Increment and decrement

int i = 5;
System.out.println(i++);   // prints 5, then i becomes 6
System.out.println(++i);   // i becomes 7, then prints 7

i++ uses the value first, then adds 1. ++i adds 1 first, then uses it. Both are common in loops as a short way to count.

Common mistakes

• Using = instead of ==. = assigns; == compares.
• Integer division surprise. 5 / 2 is 2, not 2.5 — use a double for decimals.
• Confusing i++ and ++i. The order of "use" and "add" differs.
• Using & for conditions. Use && and || for logic, not the bitwise &.

Summary

• Operators act on values for calculations and decisions.
• Arithmetic: + - * / % (watch integer division).
• Comparison returns true/false; == compares, = assigns.
• Logical &&, ||, ! combine conditions.
• ++ and -- increase or decrease by 1, with pre/post forms.

Next, make decisions with if-else in Java, or repeat actions with Java loops.