Table of Contents
Basic Data Structure
There are eight major data types in Java, which can be divided into numerical, character, and boolean types.
- Numerical Types
| Data Type | Size | Ranges |
|---|---|---|
| byte | 8 bit | -128 ~ 127 |
| short | 16 bit | -2^15 ~ 2^15 - 1 |
| int | 32 bit | -2^31 ~ 2^31 - 1 |
| long | 64 bit | -2^63 ~ 2^63 - 1 |
| float | 32 bit | single precision floating point type, such as 2.0f |
| double | 64 bit | higher precision floating point type, such as 2.0 |
- Character Types
| Data Type | Size | Ranges |
|---|---|---|
| char | 16 bit | Used to represent Unicode characters, 1 character = 2 bytes |
- Boolean Types
| Data Type | Size | Ranges |
|---|---|---|
| boolean | logical value | true && false |
Wrapper Types
In Java, each primitive data type has a corresponding wrapper class. Assignment and conversion between the primitive types and their corresponding wrapper classes are achieved through automatic boxing and unboxing.
| Primitive Data Types | Wrapper Classes |
|---|---|
| boolean | Boolean |
| char | Character |
| byte | Byte |
| short | Short |
| int | Integer |
| long | Long |
| float | Float |
| double | Double |
Automatic Boxing refers to automatically converting a primitive value into its corresponding object wrapper.
Unboxing is the reverse process where an object wrapper's value is converted back to its corresponding primitive type.
system diagram
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