Arrays.asList 分析

問題 一:

代碼如下:

    int [] arr = new int[5];
    arr[0]=1;
    arr[1]=2;
    arr[2]=3;
    arr[3]=4;
    arr[4]=5;
    List<int[]> list  =  Arrays.asList(arr);
    list.remove(0);

運行後 :

Exception in thread "main" java.lang.UnsupportedOperationException
	at java.util.AbstractList.remove(AbstractList.java:144)
	at test.testArr23.main(testArr23.java:18)

原因分析

Arrays.asList 返回的List類型爲 Arrays 的內部類的類型 : private static class ArrayList<E> extends AbstractList<E>

只是 最簡 實現的接口和抽象類,導致

AbstractList<E> 中未抽象方法  拋出異常<span style="font-family: Arial, Helvetica, sans-serif;">UnsupportedOperationException</span>.

類似如下:

<pre name="code" class="html">  public E set(int index, E element) {
<span style="white-space:pre">	</span>throw new UnsupportedOperationException();
    }


 
    public void add(int index, E element) {
<span style="white-space:pre">	</span>throw new UnsupportedOperationException();
    }

    public E remove(int index) {
<span style="white-space:pre">	</span>throw new UnsupportedOperationException();
    }

</pre><pre name="code" class="html">問題 一:

代碼如下:  

int[] arr = new int[5];
        arr[0] = 1;
        arr[1] = 2;
        arr[2] = 3;
        arr[3] = 4;
        arr[4] = 5;
        String[] strArr = new String[3];
        strArr[0] = "11";
        strArr[1] = "22";
        strArr[2] = "33";
<h2>       <span style="font-family:SimHei;"> List<String> strlist = Arrays.asList(strArr);
        List<int[]> arrlist = Arrays.asList(arr);
</span><span style="font-family:SimHei;">      </span></h2>        for (String j : strlist)
        {
            System.out.println(j);
        }


        for (int j : arrlist.get(0))
        {
            System.out.println(j);
        }