实例解析Java中的构造器初始化
1.初始化顺序 class Window { Window(int maker) { System.out.println("Window(" + maker + ")"); } } class House { Window window1 = new Window(1); House() { System.out.println("House()"); w3 = new Window(33); } Window window2 = new Window(2); void f() { System.out.println("f()"); } Window w3 = new Window(3); } public class OrderOfInitialization { public static void main(String[] args) { House h = new House(); h.f(); } } 运行结果: Window(1) Window(2) Window(3) House() Window(33) f() 由输出可见,w3这个引用会被初始化两次:一次在调用构造器之前,一次在调用期间(第一次引用的对象将被丢弃,并作为垃圾回收)。 2.静态数据的初始化 class Bowl { Bowl(int maker) { System.out.println("Bowl(" + maker + ")"); } void f1(int maker) { System.out.println("f1(" + maker + ")"); } } class Table { static Bowl bowl1 = new Bowl(1); Table() { System.out.println("Table()"); bowl2.f1(1); } void f2(int maker) { System.out.println("f2(" + maker + ")"); } static Bowl bowl2 = new Bowl(2); } class Cupboard { Bowl bowl3 = new Bowl(3); static Bowl bowl4 = new Bowl(4); Cupboard() { System.out.println("CupBoard()"); bowl4.f1(2); } void f3(int maker) { System.out.println("f3(" + maker + ")"); } static Bowl bowl5 = new Bowl(5); } public class StaticInitialization { public static void main(String[] args) { System.out.println("created new Cupboard() in main"); new Cupboard(); System.out.println("created new Cupboard in main"); new Cupboard(); table.f2(1); cupboard.f3(1); } static Table table = new Table(); static Cupboard cupboard = new Cupboard(); } 运行结果: Bowl(1) Bowl(2) Table() f1(1) Bowl(4) Bowl(5) Bowl(3) CupBoard() f1(2) created new Cupboard() in main Bowl(3) CupBoard() f1(2) created new Cupboard in main Bowl(3) CupBoard() f1(2) f2(1) f3(1) 从某种程度上来看,初始化是一段固定执行的代码,它不能接受任何参数。因此初始化块对同一个类所有对象所进行的初始化处理完全相同。基于这个原因,不难发现初始化块的基本用法,如果有一段初始化处理代码对所有对象完全相同,且无须接受任何参数,就可以把这段初始化处理代码提取到初始化块中。 以上就是本文关于实例解析Java中的构造器初始化的全部内容,希望对大家有所帮助。 (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |