static关键字详解

/**
 * @Description static关键字详解
 */
package com.oop.demo07;

//静态导入包~
import static java.lang.Math.PI;
import static java.lang.Math.random;

public class Test {
    public static void main(String[] args) {
        System.out.println(random());
        System.out.println(PI);
    }
}

/**
 * @Description static关键字详解
 */
package com.oop.demo07;

//static
public class Student {
    private static int age;//静态变量
    private double score;//非静态的变量

    public void run(){

    }

    public static void go(){

    }

    public static void main(String[] args) {
        /*
        Student s1 = new Student();

        System.out.println(Student.age);
        System.out.println(s1.age);
        System.out.println(s1.age);
        */

        new Student().run();
        go();
    }
}

/**
 * @Description static关键字详解
 */
package com.oop.demo07;

public class Person {

    //2:赋初值~
    {
        //代码块（匿名代码块）
        System.out.println("匿名代码块");
    }

    //1:只执行一次
    static{
        //静态代码块
        System.out.println("静态代码块");
    }

    //3
    public Person() {
        System.out.println("构造方法");
    }

    public static void main(String[] args) {
        Person person1 = new Person();
        System.out.println("==============");
        Person person2 = new Person();
    }
}