JavaSE-10.4.4【static关键字】

package day1.yppah04.p6;

/*
4.6 static

    static的概念
        static关键字是静态的意思，可以修饰【成员方法】，【成员变量】
    static修饰的特点
        1. 被类的所有对象共享，这也是我们判断是否使用静态关键字的条件
        2. 可以通过类名调用当然，也可以通过对象名调用【推荐使用类名调用】
 */

public class StudentDemo {
    public static void main(String[] args) {
        //school被static修饰前
        /*Student s1 = new Student();
        s1.name = "tom";
        s1.age = 20;
        s1.school = "qdu";
        s1.show();

        Student s2 = new Student();
        s2.name = "amy";
        s2.age = 22;
        s2.school = "qdu";
        s2.show();*/

        //school被static修饰后
        /*Student s1 = new Student();
        s1.name = "tom";
        s1.age = 20;
        s1.school = "qdu"; //school变为共享
        s1.show();

        Student s2 = new Student();
        s2.name = "amy";
        s2.age = 22;
//        s2.school = "qdu";
        s2.show();*/

        Student.school = "qdu"; //建议这样直接用类名访问
        Student s1 = new Student();
        s1.name = "tom";
        s1.age = 20;
//        s1.school = "qdu";
        s1.show();

        Student s2 = new Student();
        s2.name = "amy";
        s2.age = 22;
//        s2.school = "qdu";
        s2.show();
    }
}

package day1.yppah04.p6;

public class Student {

    public String name;
    public int age;
    public static String school;

    public void show(){
        System.out.println(name + "," + age + "," + school);
    }

}

package day1.yppah04.p7;

/*
4.7 static访问特点

    非静态的成员方法
        能访问静态的成员变量
        能访问非静态的成员变量
        能访问静态的成员方法
        能访问非静态的成员方法
    静态的成员方法
        能访问静态的成员变量
        能访问静态的成员方法
    总结成一句话就是：
        静态成员方法只能访问静态成员
 */

public class Student {

    private String name = "tom"; //非静态成员变量
    private static String school = "qdu"; //静态成员变量

    public void show1(){ //非静态成员方法

    }

    public void show2(){ //非静态成员方法
        System.out.println(name);
        System.out.println(school);
        show1();
        show3();
    }

    public static void show3(){ //静态成员方法

    }

    public static void show4(){ //静态成员方法
//        System.out.println(name); //error
        System.out.println(school);
//        show1(); //error
        show3();
    }

}