InnerClass 成员类

1. 成员类介绍

    成员类可以分为类级别成员类和对象级别成员类.

    区别:

• 类级别成员类:可以直接new出来,不用生成外部类
• 对象级别成员类:先要生成外部类后才能生成内部类.

    相同点:

    可以调用外部类的私有成员变量

1. 代码实例

两段代码在同一个包下

package inner.member;public class MemberClasses {private static String STATIC_PARAMETER = "static parameter";private String instantiate = "instantiate parameter";public MemberClasses(){System.out.println("MemberClasses");}// 加上 protected 效果一样static class StaticMemberClass{public StaticMemberClass(){System.out.println("Create Static Member Class");}public void staticeExec(){System.out.println("out static member class");// 可以调用外部类的私有成员变量System.out.println(STATIC_PARAMETER);}}// 取消 protected 效果一样protected class InstantiateMemberClass{public InstantiateMemberClass(){System.out.println("Create Instantiate Member Class");}public void instantiateExec(){System.out.println("out instantiate member class");System.out.println(STATIC_PARAMETER);// 可以调用外部类的私有成员变量System.out.println(instantiate);}}}

 

package inner.member;public class ExecMemberClasses {public static void main(String[] args) {// 调用类级别的成员类// 注意:没有生成MemberClasses对象MemberClasses.StaticMemberClass staticMemberClass = new MemberClasses.StaticMemberClass();staticMemberClass.staticeExec();System.out.println("======================");// 调用对象级别的成员类// 注意:生成了MemberClasses对象MemberClasses.InstantiateMemberClass instantiateMemberClass = new MemberClasses().new InstantiateMemberClass();instantiateMemberClass.instantiateExec();}}

 

1. this的使用使用方法

两段代码在不同包下

package inner.member;public class MemberClasses2 {private String s = "outter";private class InstantiateMemberClass{private String s = "inner";public InstantiateMemberClass(){System.out.println("Create Instantiate Member Class");}public void instantiateExec(){System.out.println("instantiateExec");}// 关键字this的使用方法public void parameterExec(String s){System.out.println("input : " + s);System.out.println("inner : " + this.s);System.out.println("outter : " + MemberClasses2.this.s);}}// 私有成员操作public void exec(){InstantiateMemberClass instantiateMemberClass = new InstantiateMemberClass();instantiateMemberClass.instantiateExec();instantiateMemberClass.parameterExec("input");}}

package inner.member.exec;import inner.member.MemberClasses2;public class ExecMemberClasses2 {public static void main(String[] args) {MemberClasses2 memberClass2 = new MemberClasses2();memberClass2.exec();}}

1. 声明抽象成员类和成员类的继承

    继承:

• 对象级的内部类只能在OutterClasses类中被另一个内部类继承.
• 类级的内部类可以被另外的类继承.

package inner.member;class OutterClasses{public class MemberClasses{}public class SubMemberClasses extends MemberClasses{}public abstract class InstantiateMemberAbstractClasses{}public class Inner extends InstantiateMemberAbstractClasses{}public static abstract class StaticMemberAbstractClasses{}public class Inner1 extends StaticMemberAbstractClasses{}public static class StaticMemberClasses{}public class Inner2 extends StaticMemberClasses{}public static final class StaticFinalMemberClasses{}}//类级的内部类可以被另外的类继承public class MemberAbstractClasses extends OutterClasses.StaticMemberAbstractClasses{}class MemberClasses3 extends OutterClasses.StaticMemberClasses{}