java泛型

Java泛型只是在编译器将[类型变量]都替换成了Object类型。在进行读取的时候，仍然是进行了强制转换。

/**
 * FileName: pair.java
 * CreateTime: 2010-8-3 下午03:31:50
 * Author: Administrator
 */
package cn.com.sky.generic;

/**
 * @author banna
 *
 */
public class Pair<T> {
	private T first;
	private T second;
	
	/**
	 * 
	 */
	public Pair(){
		first = null;
		second = null;
	}
	
	/**
	 * @return the first
	 */
	public T getFirst() {
		return first;
	}

	/**
	 * @param first the first to set
	 */
	public void setFirst(T first) {
		this.first = first;
	}

	/**
	 * @return the second
	 */
	public T getSecond() {
		return second;
	}

	/**
	 * @param second the second to set
	 */
	public void setSecond(T second) {
		this.second = second;
	}
}

/**
 * FileName: GenericMain.java
 * CreateTime: 2010-8-3 下午03:39:11
 * Author: Administrator
 */
package cn.com.sky.generic;

/**
 * @author banna
 *
 */
public class GenericMain {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Pair<String> pair = new Pair<String>();
		pair.setFirst("banna");
		pair.setSecond("wu");
		String first = pair.getFirst();
	}

}

对应的.class文件反编译结果

// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   Pair.java

package cn.com.sky.generic;


public class Pair
{

    public Pair()
    {
        first = null;
        second = null;
    }

    public Object getFirst()
    {
        return first;
    }

    public void setFirst(Object first)
    {
        this.first = first;
    }

    public Object getSecond()
    {
        return second;
    }

    public void setSecond(Object second)
    {
        this.second = second;
    }

    private Object first;
    private Object second;
}

// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) 
// Source File Name:   GenericMain.java

package cn.com.sky.generic;


// Referenced classes of package cn.com.sky.generic:
//            Pair

public class GenericMain
{

    public GenericMain()
    {
    }

    public static void main(String args[])
    {
        Pair pair = new Pair();
        pair.setFirst("banna");
        pair.setSecond("wu");
        String first = (String)pair.getFirst();
    }
}