java 内部类

1、new Outer().new Inner();

2、static： new Outer.Inner();

3、定义在方法中

1、

 1 class Outer {
 2     private int age = 24;
 3 
 4     class Inner {
 5         void print() {
 6             System.out.println(age);
 7         }
 8     }
 9 }
10 
11 public class Test {
12 
13     public static void main(String[] args) {
14         Outer outer = new Outer();
15         Outer.Inner inner = outer.new Inner();
16         inner.print();
17     }
18 
19 }

编译后的文件中有 Outer.class Test.class Outer$Inner.class

2、

 1 class Outer {
 2     private static int age = 24;
 3 
 4     static class Inner {
 5         void print() {
 6             System.out.println(age);
 7         }
 8     }
 9 }
10 
11 public class Test {
12 
13     public static void main(String[] args) {
14         Outer.Inner inner = new Outer.Inner();
15         inner.print();
16     }
17 
18 }

编译后的文件中有 Outer.class Test.class Outer$Inner.class

3、

 1 class Outer {
 2     private int age = 24;
 3 
 4     void out(final String name) {
 5         class Inner {
 6             void print() {
 7                 System.out.println(name);
 8                 System.out.println(age);
 9             }
10         }
11         new Inner().print();
12     }
13 
14 }
15 
16 public class Test {
17 
18     public static void main(String[] args) {
19         new Outer().out("crane");
20     }
21 
22 }

注意：传参的话，要用final修饰变量，final String name，否则编译出错。

编译后的文件中有 Outer.class Test.class Outer$Inner.class