Java 泛型学习（一）简单使用

import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.concurrent.ExecutionException;

public class GenericTest
{
	public static void main(String[] args)throws Exception
	{
		//泛型简单应用
		ArrayList<String> collection1 = new ArrayList<String>();
		collection1.add("abc");
		String element = collection1.get(0);
		System.out.println(element);
		
		//利用泛型省去类型转换之苦
		Constructor<String> constructor1=String.class.getConstructor(StringBuffer.class);
		String str1 = constructor1.newInstance(new StringBuffer("abc"));
		System.out.println(str1.charAt(1));		
		
		//编译器编译完成后会去掉泛型的信息，编译完成后collection1与collection2的类型是完全一样的
		ArrayList<Integer> collection2 = new ArrayList<Integer>();
		System.out.println(collection1.getClass() == collection2.getClass());
		
		//跳过编译器，向某个泛型集合中加入其他类型的数据
		collection2.getClass().getMethod("add",Object.class).invoke(collection2,"abc");
		System.out.println(collection2.get(0));
	}
}

运行结果如下：