Understanding Java Operators

Operators are special symbols that perform operations on one or more operands and produce a result. Every Java expression is built from operators, variables, and literals.

Operator Categories

Java operators fall into three categories based on the number of operands they require:

Operator Precedence

When an expression contains multiple operators, precedence determines the order of evaluation. Higher precedence operators are evaluated before lower ones.

Tip for the exam: You do not need to memorize every level, but you must know that multiplication and division bind more tightly than addition and subtraction, that ! is applied before &&, and that && binds more tightly than ||.

Evaluating Expressions with Precedence

Consider this expression:

java
int result = 2 + 3 * 4;  // result = 14, not 20

* has higher precedence than +, so 3 * 4 = 12 is evaluated first, then 2 + 12 = 14.

Use parentheses to override precedence:

java
int result = (2 + 3) * 4;  // result = 20

Associativity

When two operators have the same precedence, associativity determines the direction of evaluation.

java
int a = 10 - 3 - 2;  // left-to-right: (10 - 3) - 2 = 5, not 10 - (3 - 2) = 9

Assignment operators are right-to-left:

java
int x, y, z;
x = y = z = 5;  // right-to-left: z=5, then y=5, then x=5

Operand Types and Promotion

Before most binary operations, Java automatically promotes smaller numeric types:

• byte, short, and char are promoted to int before any binary arithmetic.
• If either operand is long, float, or double, the other operand is promoted to match.

java
byte b1 = 10;
byte b2 = 20;
// byte b3 = b1 + b2;  // compile error: result is int
int  b3 = b1 + b2;     // correct

Overview of Operator Types

The following lessons cover each category in depth:

Key Rules to Remember

• Parentheses always override precedence — use them when in doubt.
• byte and short arithmetic produces int, not byte or short.
• Unary prefix operators are right-to-left; most binary operators are left-to-right.
• Assignment has the lowest precedence of all operators.

References

• Oracle Docs — Operators (Java 21)
• OCP Oracle Certified Professional Java SE 21 Study Guide — Chapter 2