Java_Collections工具类

　　　1　　 2<span style="color: #000000">.sort(List list)排序

　　 3<span style="color: #000000">.sort(List list,Comparator comparator);排序

　　 4<span style="color: #000000">.binarySearch,搜索指定元素索引,前提列表必须有序

　　 5<span style="color: #000000">.reverse反转

　　　6<span style="color: #000000">.重新洗牌shuffle方法

　　 7.swap交换,交换两个索引位置元素,Collections.swap(list,1,2);

<span style="color: #0000ff">import<span style="color: #000000"> java.util.ArrayList;
<span style="color: #0000ff">import<span style="color: #000000"> java.util.Arrays;
<span style="color: #0000ff">import<span style="color: #000000"> java.util.Collections;
<span style="color: #0000ff">import<span style="color: #000000"> java.util.Comparator;
<span style="color: #0000ff">import<span style="color: #000000"> java.util.List;
<span style="color: #008000">/*<span style="color: #008000">

• 1.父类的引用指向子类的对象

• 2.sort(List list)排序

• 3.sort(List list,Comparator comparator);排序

• 4.binarySearch,前提列表必须有序

• 5.reverse反转

• 6.重新洗牌shuffle

• 7.swap交换,2);

• <span style="color: #808080">@author<span style="color: #008000"> Administrator

• <span style="color: #008000">*/
  <span style="color: #0000ff">public <span style="color: #0000ff">class<span style="color: #000000"> CollectionsDemo {
  <span style="color: #0000ff">public <span style="color: #0000ff">static <span style="color: #0000ff">void<span style="color: #000000"> main(String[] args) {
  List list=<span style="color: #0000ff">new<span style="color: #000000"> ArrayList();

   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;添加测试数据        </span>
   list.add("a"<span style="color: #000000"&gt;);
   list.add(</span>"b"<span style="color: #000000"&gt;);
   list.add(</span>"d"<span style="color: #000000"&gt;);
   list.add(</span>"c"<span style="color: #000000"&gt;);
   list.add(</span>"e"<span style="color: #000000"&gt;);
  
   System.out.println(Arrays.toString(list.toArray()));
   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;sort排序,升序</span>

  <span style="color: #000000"> Collections.sort(list);

   System.out.println(Arrays.toString(list.toArray()));
  
   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;使用sort降序排序</span>
   Collections.sort(list,<span style="color: #0000ff"&gt;new</span> Comparator<String><span style="color: #000000"&gt;(){
  
       @Override
       </span><span style="color: #0000ff"&gt;public</span> <span style="color: #0000ff"&gt;int</span><span style="color: #000000"&gt; compare(String o1,String o2) {
           </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt; TODO Auto-generated method stub</span>
           <span style="color: #0000ff"&gt;int</span> result=o2.length()-<span style="color: #000000"&gt;o1.length();
           </span><span style="color: #0000ff"&gt;int</span> length=result>0?<span style="color: #000000"&gt;o2.length():o1.length();
  
           </span><span style="color: #0000ff"&gt;char</span>[]a1=<span style="color: #000000"&gt;o1.toCharArray();
           </span><span style="color: #0000ff"&gt;char</span>[]a2=<span style="color: #000000"&gt;o2.toCharArray();
           </span><span style="color: #0000ff"&gt;for</span>(<span style="color: #0000ff"&gt;int</span> i=0;i<length;i++<span style="color: #000000"&gt;){
               </span><span style="color: #0000ff"&gt;if</span>(a1[i]><span style="color: #000000"&gt;a2[i]){
                   </span><span style="color: #0000ff"&gt;return</span> -1<span style="color: #000000"&gt;;
               }</span><span style="color: #0000ff"&gt;else</span> <span style="color: #0000ff"&gt;if</span>(a1[i]==<span style="color: #000000"&gt;a2[i]){
                   </span><span style="color: #0000ff"&gt;return</span> 0<span style="color: #000000"&gt;;
               }</span><span style="color: #0000ff"&gt;else</span><span style="color: #000000"&gt;{
                   </span><span style="color: #0000ff"&gt;return</span> 1<span style="color: #000000"&gt;;
               }
           }
           </span><span style="color: #0000ff"&gt;return</span><span style="color: #000000"&gt; result;
       }
   });
  
   System.out.println(Arrays.toString(list.toArray()));
   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;二分法检测元素索引</span>
   <span style="color: #0000ff"&gt;int</span> indexResult = Collections.binarySearch(list,"c"<span style="color: #000000"&gt;);
  
   System.out.println(indexResult);
  
   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;reverse反转</span>

  <span style="color: #000000"> Collections.reverse(list);
  System.out.println(Arrays.toString(list.toArray()));

   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;重新洗牌shuffle</span>

  <span style="color: #000000"> Collections.shuffle(list);
  System.out.println(Arrays.toString(list.toArray()));

   </span><span style="color: #008000"&gt;//</span><span style="color: #008000"&gt;swap交换,交换两个索引位置元素</span>
   Collections.swap(list,2<span style="color: #000000"&gt;);
   System.out.println(Arrays.toString(list.toArray()));

  }
  }