The Type Zoo: int, long, double, boolean, char, String

Java's primitive types are the raw values the CPU understands; everything else is an object.

| Type | Size | Range / use | Example | |---|---|---|---| | int | 32-bit | whole numbers ±~2.1 billion | int users = 1250; | | long | 64-bit | whole numbers, huge counts, timestamps | long fileId = 9_876_543_210L; | | double | 64-bit | decimals (default for floating point) | double price = 19.99; | | float | 32-bit | decimals, rare; needs f suffix | float r = 0.5f; | | boolean | — | true / false only | boolean active = true; | | char | 16-bit | ONE character, single quotes | char grade = 'A'; | | byte, short | 8/16-bit | memory-tight situations; rare for beginners | — |

Two details that bite everyone once:

• long literals need an L suffix: 9_876_543_210 is an int literal that does not fit, but 9_876_543_210L is fine. Underscores are just for readability.
• char uses single quotes, String double quotes: 'A' is a 16-bit character, "A" is an object. They are different types entirely.

String is not primitive — it is a class:

String greeting = "hi";       // an object with methods
int len = greeting.length();  // 2

Everything in Java is typed, checked, and documented. When in doubt: int for counting, double for measuring, boolean for deciding, String for text, long when numbers get big.

Next: constants and the conversion rules between types.