Java中静态变量、实例变量赋值

原创于 2024-12-25 11:21:26 发布 · 201 阅读

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1. 静态变量赋值流程

+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+
|           赋值情况              |        类加载阶段         |       类初始化阶段        |        静态变量赋值        |      `final`修饰          |
+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+
| 1. 声明时赋值，未`final`         | staticVar = 10            | 不需要再赋值               | staticVar = 10            | 否                          |
+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+
| 2. 声明时赋值，已`final`         | staticFinalVar = 10       | 不需要再赋值               | staticFinalVar = 10       | 是                          |
+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+
| 3. 声明时未赋值，未`final`       | staticVar = 0 (默认值)    | staticVar = 10            | staticVar = 10            | 否                          |
+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+
| 4. 声明时未赋值，已`final`       | staticFinalVar = 0 (默认值) | staticFinalVar = 10       | staticFinalVar = 10       | 是                          |
+----------------------------------+---------------------------+---------------------------+---------------------------+-----------------------------+

2.实例变量赋值流程

+------------------+----------------------------+-----------------------------+
| 阶段             | 创建对象时发生的过程        | 对应的实例变量赋值          |
+------------------+----------------------------+-----------------------------+
| **类加载阶段**   | 类加载时，静态变量初始化     | 静态变量赋值，实例变量不赋值 |
| **实例初始化**   | 对象创建时分配内存并赋默认值 | 实例变量赋默认值（例如 0，null） |
| **构造器阶段**    | 构造器调用                  | 构造器中显式赋值，覆盖默认值  |
+------------------+----------------------------+-----------------------------+