inner-classes | 易学教程

How to load nested classes in Java?

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I have the following java code: public class CheckInnerStatic { private static class Test { static { System.out.println("Static block initialized"); } public Test () { System.out.println("Constructor called"); } } public static void main (String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException { System.out.println("Inside main"); Class.forName("Test"); // Doesn't work, gives ClassNotFoundException //Test test = new Test(); // Works fine } } Why doesn't the class.forName("Test") work here while the next line works fine? MeBigFatGuy Use Outer$Nested

Example of inner classes used as an alternative to interfaces

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What I was told, which sparked my curiosity on this topic: Java gui classes can implement hundreds of Listeners and Callbacks and many books teach you to implement all these interfaces in your gui class. Alternatively, these aspects can be implemented in inner classes, so methods called by that listeners do not get mixed up. I'd like to know how to do this in ActionScript, which doesn't have inner classes, but has private classes. But, I don't think I fully realize what inner classes are about, so I'm merely trying to wrap my head around the situation where I would use them to organize a class

Practical side of the ability to define a class within an interface in Java?

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What would be the practical side of the ability to define a class within an interface in Java: interface IFoo { class Bar { void foobar () { System.out.println("foobaring..."); } } } alexpopescu I can think of another usage than those linked by Eric P: defining a default/no-op implementation of the interface. ./alex interface IEmployee { void workHard (); void procrastinate (); class DefaultEmployee implements IEmployee { void workHard () { procrastinate(); }; void procrastinate () {}; } } Yet another sample — implementation of Null Object Pattern : interface IFoo { void doFoo(); IFoo NULL_FOO

Using Inner classes in C#

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问题 What are the best practices regarding the use and structure of inner classes in C#. For instance if I have a very large base class and two large inner classes should I split them up into separate (partial class) codefiles or leave them as one very large unwieldy codefile? Also is it bad practice to have an abstract class, with a public inherited inner class? 回答1: Typically I reserve inner-classes for one of two purposes: Public classes which derive from their parent class where the parent

Static inner classes need import for annotations

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问题 So I was doing some jUnit testing and wanted to write distinct classes that had similar functionality but were small enough to write within a single class. Regardless of the decision for design it brought me to a compiler error I am not sure what the rules are for what I saw. You can imagine it would look something like package foo; @RunWith(Suite.class) @SuiteClasses({ TestClassOne.class, TestClassTwo.class }) public class TestSuite{ @RunWith(SpringJUnit4ClassRunner.class) public static

java inner/outer class questions about outer class private variables access

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I have the following java class: class Outer { private Integer a; private Long b; class Inner { public void foo() { System.out.println("a and b are " + a + " " + b); } } } when I run javap on Outer and Outer$Inner, I get the following: C:\test>javap Outer Compiled from "Outer.java" class Outer extends java.lang.Object{ Outer(); static java.lang.Integer access$000(Outer); static java.lang.Long access$100(Outer); } C:\test>javap Outer$Inner Compiled from "Outer.java" class Outer$Inner extends java.lang.Object{ final Outer this$0; Outer$Inner(Outer); public void foo(); } I have two questions: 1)

Passing final variables to anonymous classes

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In final variable passed to anonymous class via constructor , Jon Skeet mentioned that variables are passed to the anonymous class instance via an auto-generated constructor. Why would I not be able to see the constructor using reflection in that case: public static void main(String... args) throws InterruptedException { final int x = 100; new Thread() { public void run() { System.out.println(x); for (Constructor<?> cons : this.getClass() .getDeclaredConstructors()) { StringBuilder str = new StringBuilder(); str.append("constructor : ").append(cons.getName()) .append("("); for (Class<?> param

Nested Class Definition in source file

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If I have a nested class like so: class MyClass { class NestedClass { public: // nested class members AND definitions here }; // main class members here }; Currently, the definitions of MyClass are in the CPP file but the definitions for NestedClass are in the header file, that is, I cannot declare the functions/constructors in the CPP file. So my question is, how do I define the functions of NestedClass in the cpp file? If I cannot, what is the reason (and if this is the case, I have a vague idea of why this happens but I would like a good explanation)? What about structures? sje397 You can.

Allow access to but prevent instantiation of a nested class by external classes

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问题 I'm looking to define a nested class that is accessible to the container class and external classes, but I want to control instantiation of the nested class, such that only instances of the container class can create new instances of the nested class. The proceeding code should hopefully demonstrate this: public class Container { public class Nested { public Nested() { } } public Nested CreateNested() { return new Nested(); // Allow } } class External { static void Main(string[] args) {

What are the uses of inner classes in Java? Are nested classes and inner classes the same? [duplicate]

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Possible Duplicate: Java inner class and static nested class What are the uses of inner classes in Java? Are nested classes and inner classes the same? polygenelubricants No, they're not the same: an inner class is non- static . JLS 8.1.3 Inner Classes and Enclosing Instances An inner class is a nested class that is not explicitly or implicitly declared static. Consult also the following diagram from Joe Darcy: Joseph D. Darcy's Oracle Weblog - Nested, Inner, Member, and Top-Level Classes Related questions Java inner class and static nested class ewernli The difference is well addressed by the