java——类的学习（2）

类的属性组使用

public class class_attributes {
         static String a = "string-a";
         static String b;
         String c="string_c";
         String d;
         
         static {
             printStatic("before static");
             b="string_b";
             printStatic("after static");
         }
         
         public static void printStatic(String title) {
             System.out.println("---------"+title+"---------");
             System.out.println("a = ""+a+""");
             System.out.println("b = ""+b+""");
         }
         
         public class_attributes(){
             print("before constructor");
             d="string_d";
             print("after constructor");
         }
         
         public void print(String title) {
             System.out.println("---------"+title+"---------");
             System.out.println("a = ""+a+""");
             System.out.println("b = ""+b+""");
             System.out.println("c = ""+c+""");
             System.out.println("d = ""+d+""");
         }
         
          public static void main(String args[]) {
             new  class_attributes();
         }
}

---------before static---------
a = "string-a"
b = "null"
---------after static---------
a = "string-a"
b = "string_b"
---------before constructor---------
a = "string-a"
b = "string_b"
c = "string_c"
d = "null"
---------after constructor---------
a = "string-a"
b = "string_b"
c = "string_c"
d = "string_d"

由此可以看出java类属性和对象属性的初始化顺序如下：

1.类属性定义时的初始化

2.static块中的初始化代码

3.对象属性定义时的初始化

4.构造方法中的初始化代码