How to use non-access control modifiers in Java?

1. The static modifier is used to modify methods and class variables.

2. The final decorator is used to decorate methods and variables.

Final decorated categories cannot be inherited, and decorated methods cannot be redefined. Decorated variables are constants and cannot be modified.

3. abstract modifier, used to create abstractions and abstract methods.

4, synchronized and volatile modifiers are mainly used for programming threads.

Example

public class Test {
     // 定义变量时制定初始化值
     final String f = "你好";
     static final String w = "大家好" ;
     // final修饰的变量必须显示初始化
     static final int a;
     final int b ;
     final int c ;
     // 在静态代码块中初始化
     static {
           a = 100;
           // 静态代码块中不能初始化实例变量
           // b=15;
     }
     // 在普通代码块中初始化
     {
           b = 100;
     }
 
     // 在构造器中初始化
     public Test( int c) {
           this.c = c;
     }
 
     // 成员变量只能在以上几个地方执行初始化，所以final修饰的变量只能在这几个地方初始化
     // 初始化结束，这些语句将不会再执行
     public static void main(String args[]) {
           // final修饰的变量第一次被赋初始值后，不可以再改变
           // 为final变量再次赋值，将出现错误。
           // Test.a=1000;
          Test test = new Test(80);
          System. out.println(test.c );
           // 为final修饰的实例变量再次赋值，将出现错误
           // test.c=60;
 
     }
 
}

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