Arrays.asList 分析

问题 一:

代码如下:

 

    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);

运行后 :

 

 

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类型为 Arrays 的内部类的类型 : private static class ArrayList<E> extends AbstractList<E>

只是 最简 实现的接口和抽象类,导致

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

类似如下:

<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">问题 一:

代码如下:

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);
    }