Java_静态Static

package cn.ALAN_CF.studyf008;
/**
 * @author 15328
 */
public class Main {
    public static void main(String[] args) {
        HeaderMaster hm1 = HeaderMaster.getHeaderMaster();
        System.out.println(hm1);
        HeaderMaster hm2 = HeaderMaster.getHeaderMaster();
        System.out.println(hm2);
        System.out.println(hm1 == hm2);
        //只有一个HeadMaster对象，hm1和hm2先后成为他的引用
    }
}
class HeaderMaster{
    private static HeaderMaster hm = null;
    private static  String NAME_OF_HM = "fist";
    /**类外无法访问该私有的静态成员*/
    public static HeaderMaster getHeaderMaster(){//静态方法
        if(hm == null) {
            hm = new HeaderMaster();
            NAME_OF_HM = "fist_head";
        }
        else {
            NAME_OF_HM ="影子，依旧是first_head";
        }
        return hm;
    }
    private HeaderMaster(){

    }

    @Override
    public String toString() {
        return this.NAME_OF_HM;
    }
}

package cn.ALAN_CF.studyf008;
/**
 * @author 15328
 * 接口允许带有常量(final)的字段
 */
public class Mainx {
    public static void main(String[] args) {
        Student p = new Student();
        System.out.println("Person.count: " + Person.count);
        System.out.println("Person.count2: " + Person.count2);
        System.out.println("Person.count3: " + Person.count3);
        System.out.println("p.count: " + p.count);
        System.out.println("p.count2: " + p.count2);
        System.out.println("p.count3: " + p.count3);
    }
}
interface Person{
    final int count = 99;
    public static  final int count3 = 999999;
    public static int count2 =9999;
    //非法操作：protected  static  int count2 =9999;
    // java: 此处不允许使用修饰符protected
}
class Student implements Person{

}