Primitives: every key term you need

Java Primitives

Basic data types: int, double, boolean, char. Store actual values (not references). Eight primitive types total.

int Type

32-bit integer; range ≈ -2 billion to +2 billion. Used for counting, indexing, calculations without decimals.

double Type

64-bit floating-point; represents decimal numbers. Used for precise calculations, measurements, divisions.

boolean Type

True or false; result of comparisons. Used in conditionals (if/else), loops. Single bit conceptually.

char Type

Single character: 'A', '5', '!'. Uses Unicode encoding. Enclosed in single quotes (different from String double quotes).

Type Casting

Convert between types: (int) 3.7 → 3 (truncates). (double) 5 → 5.0. Widening (small to large) safe; narrowing (large to small) risky.

Implicit Type Conversion

Java automatically widens types (int to double). Narrowing requires explicit cast. Math operations promote to larger type.

Arithmetic Operators

+ (add), - (subtract), * (multiply), / (divide), % (modulo/remainder). Precedence: *, /, % then +, -. Left-to-right for same precedence.

Modulo Operator %

Returns remainder: 7 % 3 = 1. Useful for: divisibility checks, cycling values, extracting digits.

Integer Division

5 / 2 = 2 (not 2.5) in Java. One or both operands must be double for decimal result: 5 / 2.0 = 2.5.

Variable Declaration

type name; or type name = value;. Example: int age; int age = 25;. Must declare before using.

Naming Conventions

Variables: camelCase starting lowercase. Constants: ALL_CAPS. Descriptive names improve readability.

Comparison Operators

== (equal), != (not equal), < (less), > (greater), <= (less/equal), >= (greater/equal). Return boolean.

Logical Operators

&& (AND), || (OR), ! (NOT). Used in compound conditions. Short-circuit: && stops if first false, || stops if first true.

Order of Operations

1. Parentheses, 2. Multiplication/Division/Modulo, 3. Addition/Subtraction, 4. Comparison, 5. Logical operators.

String Type (Not Primitive)

String class (capital S) for text. String s = \"Hello\"; Reference type, not primitive. Immutable.

Unit 1 Summary

Primitives: int, double, boolean, char. Casting converts types. Operators: arithmetic (+,-,*,/,%), comparison, logical. Variables store data.

More AP Computer Science A guides

• Using Objects
• Boolean Expressions
• Loops
• Writing Classes
• Arrays