java中两种有趣的匿名种实现

java中两种有趣的匿名类实现

java中的匿名类除了还有两种有趣的用法

/**
 * TODO Comment of AnonymousTest
 * 
 * @author aotian.zhuw
 */
class EntryInterface {

    public void print() {
        System.out.println("hello world");

    }

}

public class AnonymousTest {

    private EntryInterface a;

    public void setA(EntryInterface a) {
        this.a = a;
    }

    public void print() {
        a.print();

    }

    public static void main(String[] args) {
        AnonymousTest test = new AnonymousTest();
        test.setA(new EntryInterface() {

            public void print() {
                System.out.println("test success.");
            }
        });
        test.print();
    }
}

首先看上面的代码我们在setA中传入的是一个匿名类

编译之后得到三个文件EntryInterface.class AnonymousTest.class AnonymousTest$1.class

反编译AnonymousTest$1.class文件，得到的结果如下

package cn.zw;

import java.io.PrintStream;

// Referenced classes of package cn.zw:
//            EntryInterface, AnonymousTest

static class AnonymousTest$1 extends EntryInterface
{

    public void print()
    {
        System.out.println("test success.");
    }

    AnonymousTest$1()
    {
    }
}

结果我们发现，java的编译器自动创建了一个EntryInterface的子类，

名为AnonymousTest$1,且该类覆盖了父类的print()方法。

修改AnonymousTest类

interface EntryInterface {

    public void print();

}

public class AnonymousTest {

    private EntryInterface a;

    public void setA(EntryInterface a) {
        this.a = a;
    }

    public void print() {
        a.print();

    }

    public static void main(String[] args) {
        AnonymousTest test = new AnonymousTest();
        test.setA(new EntryInterface() {

            public void print() {
                System.out.println("test success.");
            }
        });
        test.print();
    }
}

编译之后仍旧得到三个文件EntryInterface.class AnonymousTest.class AnonymousTest$1.class

反编译AnonymousTest$1.class文件，得到的结果如下

import java.io.PrintStream;

// Referenced classes of package cn.zw:
//            EntryInterface, AnonymousTest

static class AnonymousTest$1
    implements EntryInterface
{

    public void print()
    {
        System.out.println("test success.");
    }

    AnonymousTest$1()
    {
    }
}

这次我们发现编译器创建的AnonymousTest$1类实现了EntryInterface接口，很有趣。

java中两种有趣的匿名种实现

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