static解析

Static详解

package oop.Test06;
​
public class Student {
    private static int age;//静态变量 多线程会用到
    private double score;//非静态变量
    public  void run(){
​
    }
    public static void go(){
​
    }
​
​
    public static void main(String[] args) {
        go();
        Student.go();
        Student student=new Student();
        System.out.println(Student.age);
        System.out.println(student.score);
        System.out.println(student.score);
        student.run();
       /* System.out.println(Student.score);*/
    }
​
}
​

 

package oop.Test06;
​
public class Person {
    {
        //代码块(匿名代码块)
        System.out.println("匿名代码块");
    }
    static {
​
        System.out.println("静态代码块");
        //静态代码块
    }
    public Person(){
        System.out.println("构造方法");
    }
​
    public static void main(String[] args) {
        Person person=new Person();
        System.out.println("=====================================================");
        Person p1=new Person();//static中的内容只执行一次.
    }
}
​

结果
    "C:\Program Files\Java\jdk1.8.0_291\bin\java.exe" "-javaagent:D:\Myidea\IntelliJ IDEA 2020.1.4\lib\idea_rt.jar=57062:D:\Myidea\IntelliJ IDEA 2020.1.4\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_291\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_291\jre\lib\rt.jar;D:\JavaSEproject\out\production\Java基础语法" oop.Test06.Person
静态代码块
匿名代码块
构造方法
=====================================================
匿名代码块
构造方法
​
Process finished with exit code 0
​

package oop.Test06;
import static java.lang.Math.random;//静态导入包
import static java.lang.Math.PI;
public class Application {
    public static void main(String[] args) {
        System.out.println(random());
        System.out.println(PI);
    }
}//不用写Math.了
//final之后无子类,断子绝孙!