java继承 初始化顺序

 

java继承 初始化顺序

标签： 初始化顺序

2013-08-01 10:13 879人阅读 评论(0) 收藏 举报

 分类：

java（8） 

版权声明：本文为博主原创文章，未经博主允许不得转载。

package Study.Initialization;

class Base{
    private String str1=init("str1");
    private String str2=init("str2");
    public static String str3=init("static str3");

    public Base(String str1,String str2){
        System.out.println("Run Construction Base");
        this.str1=str1;
        this.str2=str2;
    }

    protected static String init(String str){
        System.out.println(str);
        return str+" init";
    }
}

class Derived extends Base{
    private String str4=init("str4");
    public static String str5=init("static str5");
    public Derived(String str1,String str2,String str4){
        super(str1,str2);
        System.out.println("Run Construction Derived");
        this.str4=str4;
    }
}

public class extendInitialization {
    public static void main(String[] args) {
        System.out.println("run extendInitialization.main()");
        Derived d=new Derived("construction str1","construction str2","construction str4");
        System.out.println("----------------------------------------");
        Derived d2=new Derived("construction str11","construction str22","construction str44");
    }

}

运行结果:

run extendInitialization.main()
static str3
static str5
str1
str2
Run Construction Base
str4
Run Construction Derived
----------------------------------------
str1
str2
Run Construction Base
str4
Run Construction Derived
总结:
   Derived的初始化顺序:
    1.按定义时的顺序初始化基类的static成员
    2..按定义时的顺序初始化扩展类的static成员
    (以上两条是对第一次定义扩展类对象时运行)
    3.按定义时顺序执行基类的指定初始化
    4.执行基类的构造函数 
    5 按定义时的顺序执行扩展类的指定初始化
    6.行扩展类的构造函数