java 泛型与反射 一个小例子

来源：QQ中的qun

package com.common.dao;

interface DBDao
{
	public int delete();
}
class Table1 implements DBDao 
{
	public int delete() 
	{
		System.out.println("Table1.delete");
		return 0;
	}
}
class Table2 implements DBDao 
{
	public int delete() 
	{
		System.out.println("Table2.delete");
		return 0;
	}	
}
public class Factory 
{
	public static void main(String args[])
	{	
		Factory.getInstance("com.common.dao.Table1").delete();
		Factory.getInstance("com.common.dao.Table2").delete();
	}
	public static <U extends DBDao>U getInstance(String clsName)
	{
	        try
	        {
	               Class cls = Class.forName(clsName);
	               return (U) cls.newInstance();
	        }
	        catch(Exception e)
	        {
	               e.printStackTrace();
	               return null;
	        }
	}	
}

与下面的不用范型效果一样

package com.common.dao;

interface DBDao
{
	public int delete();
}
class Table1 implements DBDao 
{
	public int delete() 
	{
		System.out.println("Table1.delete");
		return 0;
	}
}
class Table2 implements DBDao 
{
	public int delete() 
	{
		System.out.println("Table2.delete");
		return 0;
	}	
}
public class Factory 
{
	public static void main(String args[])
	{	
		((DBDao)Factory.getInstance("com.common.dao.Table1")).delete();
		((DBDao)Factory.getInstance("com.common.dao.Table2")).delete();
		
	}
	public static Object getInstance(String clsName)
	{
	        try
	        {
	               Class cls = Class.forName(clsName);
	               return  cls.newInstance();
	        }
	        catch(Exception e)
	        {
	               e.printStackTrace();
	               return null;
	        }
	}	
}