Inner Class

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Inner Class

内部类

  1. 内部类共分为4种：

  • 静态内部类(static inner class):只能访问外部类的静态成员变量与静态方法，生成静态内部类对象的方式为：OuterClass.InnerClass inner = new uterClass.InnerClass()

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    class StaticInner {
        private static int a = 4;
        public static class Inner{
            public void test() {
                System.out.println(a);
            }
        }
    }
    class StaticInnerTest {
        public static void main(String[] args) {
            StaticInner.Inner inner = new StaticInner.Inner();
            inner.test();
        }
    }

  • 成员内部类(menber inner class):可以访问外部类的静态与非静态的方法与成员变量。生成成员内部类对象的方式为：MemberInner.Inner2 inner2 = new MemberInner().new Inner2();

  • 若想在局部内部类中访问外部类成员变量，语法为：
    OuterClass.this.a;

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    class MemberInner {
        private int a = 4;
        public class Inner2{
            private int a = 5;
            public void doSomething() {
                //访问外部类属性
                System.out.println(MemberInner.this.a);
            }
        }
    }
    class MemberInnerTest {
        public static void main(String[] args) {
            MemberInner.Inner2 inner2 = new MemberInner().new Inner2();
            inner2.doSomething();
        }

  • 局部内部类(Local Inner Class):定义在方法当中，只能访问方法中声明的final类型的变量。

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    public class LocalInnerClass {
        public void doSomething() {
            final int b = 4;
            class Inner3 {
                public void test() {
                    System.out.println(b);
                }
            }
            new Inner3().test();
        }
    }
    class LocalInnerClassTest {
        public static void main(String[] args) {
            LocalInnerClass localInnerClass = new LocalInnerClass();
            localInnerClass.doSomething();
        }
    }

  • 匿名内部类(g):匿名内部类会隐式地集成一个父类或实现一个接口。

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    public class AnonymousInnerClass {
        @SuppressWarnings(value = "deprecation")
        public String get(Date date) {
            return date.toLocaleString();
        }
        public static void main(String[] args) {
            AnonymousInnerClass anonymousInnerClass = new AnonymousInnerClass();
    //        String str =  anonymousInnerClass.get(new Date());
    //        System.out.println(str);
            //匿名内部类继承了date类
            String str =  anonymousInnerClass.get(new Date(){
                @Override
                public String toLocaleString() {
                    return "hello world";
                }
            });
            System.out.println(str);
        }
    }