JAVA中的static用法

JAVA中static用法的几个关键点:

 

1.类中的static变量在类加载时首先被初始化,且只能初始化一次.

2.所有对象共享类中的static变量.

3.在创建子类的对象时,先初始化父类的static变量,再初始化子类的static.

实例如下:

public class A
{
 static
 {
  System.out.println("I'm in class A's static!");
 }

 public A()
 {
  System.out.println("I'm in class A's structure!");
 } 
};

public class B extends A
{
 static
 {
  System.out.println("I'm in class B's static!");
 }

 public B()
 {
  System.out.println("I'm in class B's structure!");
 }
};

public class TestStatic
{
 public static void main(String[] arg)
 {
  A ab = new B();
  B ba = new B();
 }
};

输出结果为:

I'm in class A's static!
I'm in class B's static!
I'm in class A's structure!
I'm in class B's structure!
I'm in class A's structure!
I'm in class B's structure!