Java static

 

include static block, static method, static variable

public class Test ...{

 
    public static void main(String[] args)  ...{
    // 调用静态方法
    staticTest();
    }
    
    /**//**
     * 静态方法的调用
     */
    private static void staticTest() ...{
    
    Apple a = new Apple();
    System.out.println(a.count);
    
    a.count = 20;
    
    System.out.println("second phrase");
    Apple b = new Apple();
    System.out.println(a.count);
    System.out.println(b.count);
    
    System.out.println("third phrase");
    Apple c = new Apple();
    System.out.println(a.count);
    System.out.println(b.count);
    System.out.println(c.count);
    
    System.out.println("four phrase");
    Apple d = new Apple(100);
    System.out.println(a.count);
    System.out.println(b.count);
    System.out.println(c.count);
    System.out.println(d.count);
    
    // 直接调用类的静态方法
    d.setCount(1000);
    System.out.println(a.count);
    System.out.println(b.count);
    System.out.println(c.count);
    System.out.println(d.count);
    }

}

class Apple...{
    
    public static int count = 2;
    
    /**//**
     * 静态初始化块,随着类进行初始化工作
     */
    static ...{
    System.out.println(count);
    count = 10;
    System.out.println("static block test");
    System.out.println(count);
    }
    
    /**//**
     * 构造函数
     */
    public Apple() ...{
    count++;
    System.out.println("Apple number: "+count);
    }
    
    /**//**
     * 类的static块
     */
    static ...{
    System.out.println("static end");
    }
    
    /**//**
     * 带参数的构造函数
     * @param initCount
     */
    public Apple(int initCount)...{
    this.count = initCount;
    }
    
    /**//**
     * 调用静态初始化
     * @param i
     */
    public static void setCount(int i) ...{
    count = i;
    }
}

 

run results:

2
static block test
10
static end
Apple number: 11
11
second phrase
Apple number: 21
21
21
third phrase
Apple number: 22
22
22
22
four phrase
100
100
100
100
1000
1000
1000
1000

 Another example:

 

import java.util.Arrays;



public class Test ...{

 
    public static void main(String[] args)  ...{


    Temp.i = 192;
    System.out.println(Temp.i);
    
    Temp t = new Temp();
    System.out.println(t.i);
    }
        

}

class Temp ...{
    
    static ...{
    i = 10;
    }
    
    public static int i ;
    
    static...{
    System.out.println(i);
    i++;
    System.out.println(i);
    }
}

run results:

10
11
192
192

 

To summary: Class init the static var when class init only once, then the var become global, and the static should be accessed only in static but not absolutly. and static method can be called by using Class name, and static method invoke static method....