浅谈Arrays.asList() 和ArrayList类型区别

<pre name="code" class="html">自己测试：<span>	</span>//arrayList
<span>		</span>List list = new ArrayList();
<span>		</span>list.add("yz_b_insert");
<span>		</span>list.add("yz_b_del");
<span>		</span>list.add("yz_b_update");
<span>		</span>list.add("yz_b_see");
<span>		</span>System.out.println(list.contains("yz_b_update")+"=="+list);
<span>		</span>//arrays.asList()
<span>		</span>String dd = "yz_b_insert,yz_b_del,yz_b_update,yz_b_see";
<span>		</span>List list2 = Arrays.asList(dd);
<span>		</span>System.out.println(list2.contains("yz_b_update")+"@@@@@"+list2);

<pre name="code" class="html">arraylist：true==[yz_b_insert, yz_b_del, yz_b_update, yz_b_see]
<pre name="code" class="html">arrays.asList()：false@@@@@[yz_b_insert,yz_b_del,yz_b_update,yz_b_see]

<span style="color: rgb(102, 102, 102); font-family: Tahoma;">为什么Arrays.asList产生的List是不可添加或者删除，否则会产生UnsupportedOperationException，就可以得到解释了。 </span><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><span style="color: rgb(102, 102, 102); font-family: Tahoma;">如果我们想把一个变长或者数据转变成List， 而且期望这个List能够进行add或者remove操作，那该怎么做呢？ </span><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><span style="color: rgb(102, 102, 102); font-family: Tahoma;">我们可以写一个类似的方法，里面直接采用java.util.ArrayList即可。 </span><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><span style="color: rgb(102, 102, 102); font-family: Tahoma;">比如： </span><br style="color: rgb(102, 102, 102); font-family: Tahoma;" /><pre class="java" name="code" style="color: rgb(102, 102, 102); background-color: rgb(255, 255, 255);">import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class MyArrays {
	public static <T> List<T> asList(T... a) {
		List<T> list = new ArrayList<T>();
		Collections.addAll(list, a);
		return list;
	}
}

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Test {
	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");
		print(stooges);
		List<List<String>> seasonsList = Arrays.asList(retrieveSeasonsList());
		print(seasonsList);
		/*
		 * 自己实现一个asList方法，能够添加和删除。
		 */
		List<String> list = MyArrays.asList("Larry", "Moe", "Curly");
		list.add("Hello");
		print(list);
	}
	private static <T> void print(List<T> list) {
		System.out.println(list);
	}
	private static List<String> retrieveSeasonsList() {
		List<String> seasonsList = new ArrayList<String>();
		seasonsList.add("Spring");
		seasonsList.add("Summer");
		seasonsList.add("Autumn");
		seasonsList.add("Winter");
		return seasonsList;
	}
}