static关键字详解

static关键字详解

static作为静态代码块

package oop.demo01.demo07;

import javax.swing.plaf.synth.SynthOptionPaneUI;

//static
public class Student {
    private  static  int age;//静态变量 可调用静态方法里的。不可调用非静态的
    private  double  score;//非静态变量  可调用静态方法里的
    public void  run(){
        go();
    }
    public static void go(){

    }
    public static void main(String[] args) {
  go();
    }
}

package oop.demo01.demo07;

public class Person {
    {//2:赋初始值
        System.out.println("匿名代码块");
    }
    //1:只执行一次
    static {
        System.out.println("静态代码块");
    }
    public Person(){//3
        System.out.println("构造方法");
    }
    public static void main(String[] args){
      Person person1=  new Person();
        System.out.println("=======================");
        Person person2=  new Person();
    }
}

静态导入包

package oop.demo01.demo07;
//静态导入包
import static java.lang.Math.random;
import static java.lang.Math.PI;
public class Test {
    public static void main(String[] args) {
        System.out.println(random());
        System.out.println(PI);
    }
}