Java-泛型编程-类型擦除(Type Erasure)

标签：java   泛型   虚拟机   反编译   

（实际上Comparable也是一个泛型接口，所以最正确的定义方法是public static <T extends Comparable<? super T>> T min(T[] a)  )

public class Pair<T> {
    private T first;
    private T second;

    public Pair(T first, T second) {
        this.first = first;
        this.second = second;
    }

    public T getFirst() {
        return first;
    }

    public T getSecond() {
        return second;
    }

    public void setFirst(T newValue) {
        first = newValue;
    }

    public void setSecond(T newValue) {
        second = newValue;
    }
}

public class Pair {
    private Object first;
    private Object second;

    public Pair(Object first, Object second) {
        this.first = first;
        this.second = second;
    }

    public Object getFirst() {
        return first;
    }

    public Object getSecond() {
        return second;
    }

    public void setFirst(Object newValue) {
        first = newValue;
    }

    public void setSecond(Object newValue) {
        second = newValue;
    }
}

class DateInterval extends Pair<Date> {
    public DateInterval(Date first, Date second) {
        super(first, second);
    }
    
    public void setSecond(Date second) {
        if (second.compareTo(getFirst()) >= 0) {
            super.setSecond(second);
        } else {
            throw new IllegalArgumentException("Second date should be no earlier than first date.");
        }
    }
    
    public Date getSecond() {
        return (Date) super.getSecond().clone();
    }
}

可以使用Jad工具来反编译class文件，就能清除到看到编译器所做的工作。
例如运行jad.exe DateInterval.class，生成下面的反编译文件

// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   Pair.java

package learning.generic;

import java.util.Date;

// Referenced classes of package learning.generic:
//            Pair

class DateInterval extends Pair
{

    public DateInterval(Date first, Date second)
    {
        super(first, second);
    }

    public void setSecond(Date second)
    {
        if(second.compareTo((Date)getFirst()) >= 0)
            super.setSecond(second);
        else
            throw new IllegalArgumentException("Second date should be no earlier than first date.");
    }

    public Date getSecond()
    {
        return (Date)((Date)super.getSecond()).clone();
    }

    public volatile void setSecond(Object obj)
    {
        setSecond((Date)obj);
    }

    public volatile Object getSecond()
    {
        return getSecond();
    }
}

Java-泛型编程-类型擦除(Type Erasure)

标签：java   泛型   虚拟机   反编译   

原文地址：http://blog.csdn.net/fw0124/article/details/42295463