java中一切皆對象，那就從對象初始化開始說起。

示例代碼：

 1 package test;
 2 
 3 public class A extends B {
 4 
 5     int i;
 6     static int b;
 7     public D firstD = new D("A");
 8     public static C firstC = new C("A");
 9     public static C secondC;
10     {
11         System.out.println("i:"+i);//此時i未初始化，為默認值0
 
12         System.out.println("b:"+b);
13         System.out.println(secondC);
14     }
15     A(){
16         
17         System.out.println("here is A");
18         i = 1;
19         b = 1;
20     }
21     
22     public static void main(String[] args) {
23         // TODO 自動生成的方法存根
24         new
 
 A();
25     }
26 
27 }
28 
29 class B {
30     public static C CinB = new C("B");
31     public D DinB = new D("B");
32     B(){
33         System.out.println("here is B");
34     }
35 }
36 
37 class C {
38     C(String source){
39         System.out.println("here is C from"+source);
 
40     }
41 }
42 
43 class D {
44     D(String source){
45         System.out.println("here is D from"+source);
46     }
47 }

輸出：

here is C fromB
here is C fromA
here is D fromB
here is B
here is D fromA
i:0
b:0
null
here is A

結論：

1.在初始化時，首先為對象分配一塊存儲空間(默認為二進制0)

2.初始化順序：基類靜態成員->子類靜態成員->基類非靜態成員/實例初始化->基類構造器->子類非靜態成員/實例初始化->子類構造器

java初始化