Java内部类的定义及在外部使用的方法

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1、静态内部类

public class Outer {static class StaticInner{public void show() {System.out.println("StaticInner");}}public static void main(String[] args) {Outer.StaticInner inner = new Outer.StaticInner();inner.show();}}

2、实例内部类（非静态内部类）

public class Outer {class MemberInner{public void show() {System.out.println("MemberInner");}}public static void main(String[] args) {Outer outer = new Outer();Outer.MemberInner inner = outer.new MemberInner();inner.show();}}

3、静态内部类访问嵌套它的外部类的静态成员

public class Outer {private static int sa = 5;private int ia = 10;static class StaticInner{public void show() {//静态内部类可以访问嵌套它的外部类的静态成员System.out.println("Outer's sa = " + sa);//Error。静态内部类不能访问嵌套它的外部类的实例成员//System.out.println("Outer's ia = " + ia);}}public static void main(String[] args) {Outer.StaticInner inner = new Outer.StaticInner();inner.show();}}

4、实例内部类访问嵌套它的外部类的成员

public class Outer {private static int sa = 5;private int ia = 10;class MemberInner{public void show() {System.out.println("Outer's sa = " + sa);System.out.println("Outer's ia = " + ia);}}public static void main(String[] args) {Outer outer = new Outer();Outer.MemberInner inner = outer.new MemberInner();inner.show();}}

5、内部类跟嵌套它的外部类属性重名时的访问方法

public class Outer {private static int sa = 1;private int ia = 2;static class StaticInner{private static int sa = 10;private int ia = 20;public void show() {System.out.println("From StaticInner: Outer's sa = " + Outer.sa);System.out.println("From StaticInner: StaticInner's ia = " + ia);}}class MemberInner{//Error。实例内部类中不能有非常量的静态属性//private static int ta = 1000;private static final int ta = 100;private int ia = 200;//Error。实例内部类中也不能有静态的方法/*public static void nothing() {}*/public void show() {System.out.println("From MemberInner: Outer's sa = " + Outer.sa);System.out.println("From MemberInner: Outer's ia = " + Outer.this.ia);System.out.println("From MemberInner: MemberInner's sa = " + MemberInner.ta);System.out.println("From MemberInner: MemberInner's ia = " + this.ia);}}public static void main(String[] args) {Outer.StaticInner si = new Outer.StaticInner();si.show();Outer.MemberInner mi = new Outer().new MemberInner();mi.show();}}

6、方法中定义的内部类

public class Outer {private static String staticOuterMsg = "static outer message";private String memberOuterMsg = "member outer message";public void show(String argMsg) {String normalLocalMsg = "normal local message";final String finalLocalMsg = "final local message";class Inner{public void print() {System.out.println(staticOuterMsg);System.out.println(memberOuterMsg);System.out.println(finalLocalMsg);//Error。方法中的内部类只能访问final局部变量//System.out.println(normalLocalMsg);//Error。方法中的内部类只能访问final局部变量。//System.out.println(argMsg);}}new Inner().print();}public static void main(String[] args) {new Outer().show("argument message");}}

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