Day10_java面向对象 static关键字详解

static关键字详解

package com.oop.demo07;

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

    public void run(){
        go();
    }
    public static void go(){
        System.out.println("hh");
    }
    public static void main(String[] args) {
        go();

        Student s1 = new Student();

        System.out.println(Student.age);
        System.out.println(s1.score);
        System.out.println(s1.age);
    }

}

package com.oop.demo07;

public class Person {

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

    //1.只执行一次
    static {
        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 person = new Person();
        System.out.println("===============");
        Person person1 = new Person();
    }


}

通过final修饰的类没有子类

package com.oop.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);
    }
}