41.static关键字详解

Static关键字详解

package com.ninglei;
​
//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(Math.random());
        System.out.println(random());
        System.out.println(PI);
​
    }
​
}
​

package com.ninglei;
​
//static :
public class Student {
​
    private static int age; //静态变量
    private double score; //非静态变量
​
    public void run(){
​
    }
    public static void go(){
​
    }
​
    public static void main(String[] args) {
        Student student = new Student();
        System.out.println(Student.age);
//        System.out.println(Student.score);
        System.out.println(student.age);
        System.out.println(student.score);
​
        Student student1 = new Student();
        student1.run();
        Student.go();
​
​
    }
}

package com.ninglei;
​
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 person = new Person();
        System.out.println("=========================");
        Person person2 = new Person();
​
    }
​
}
​