import java.util.ArrayList;

 import java.util.List;

 /**

  * 集合操作

  * @author intrl

  * @date 2010-12-15

  * @version 1.0

  */

 public class Test {

     public static void main(String[] args) {

         List<String> list=new ArrayList<String>();

         list.add("aaa");

         list.add("bbb");

         list.add("ccc");

         System.out.println(listToString(list));//aaa,bbb,ccc

     }

     public static String listToString(List<String> stringList){

         if (stringList==null) {

             return null;

         }

         StringBuilder result=new StringBuilder();

         boolean flag=false;

         for (String string : stringList) {

             if (flag) {

                 result.append(",");

             }else {

                 flag=true;

             }

             result.append(string);

         }

         return result.toString();

     }

 }

 这代码太垃圾了

 为什么不

 int length = arr.length ;

 StringBuffer buf = new StringBuffer("");

 if(length > 0){

     buf.append(arr[0]);

 }

 for(int i = 1 ; i < length ; i++){

    buf.append(',');

    buf.append(arr[i]);

 }

 public static String join(Iterator iterator, String separator) {

         // handle null, zero and one elements before building a buffer

         if (iterator == null) {

             return null;

         }

         if (!iterator.hasNext()) {

             return EMPTY;

         }

         Object first = iterator.next();

         if (!iterator.hasNext()) {

             return ObjectUtils.toString(first);

         }

         // two or more elements

         StringBuffer buf = new StringBuffer(256); // Java default is 16, probably too small

         if (first != null) {

             buf.append(first);

         }

         while (iterator.hasNext()) {

             if (separator != null) {

                 buf.append(separator);

             }

             Object obj = iterator.next();

             if (obj != null) {

                 buf.append(obj);

             }

         }

         return buf.toString();

     }