java - 优化这个ArrayList的join方法

Question

我编写了这段代码来连接 ArrayList 元素:能再优化一下吗？或者有更好的不同方法吗？

public static String join(ArrayList list, char delim) {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < list.size(); i++) {
            if (i != 0)
                buf.append(delim);
            buf.append((String) list.get(i));
        }
        return buf.toString();
    }

Answer 1

Here著名的 java.util.Collection 团队就是这样做的，所以我认为这应该非常好 ;)

  421       /* Returns a string representation of this collection.  The string
  422        * representation consists of a list of the collection's elements in the
  423        * order they are returned by its iterator, enclosed in square brackets
  424        * (<tt>"[]"</tt>).  Adjacent elements are separated by the characters
  425        * <tt>", "</tt> (comma and space).  Elements are converted to strings as
  426        * by {@link String#valueOf(Object)}.
  427        *
  428        * @return a string representation of this collection
  429        */
  430       public String toString() {
  431           Iterator<E> i = iterator();
  432           if (! i.hasNext())
  433               return "[]";
  434   
  435           StringBuilder sb = new StringBuilder();
  436           sb.append('[');
  437           for (;;) {
  438               E e = i.next();
  439               sb.append(e == this ? "(this Collection)" : e);
  440               if (! i.hasNext())
  441                   return sb.append(']').toString();
  442               sb.append(", ");
  443           }

此外，这就是您将如何使用 duffymo 的答案获得逗号分隔符；)