public static String convert(String[] a) {
if (a == null || a.length==0) return null;
StringBuffer s = new StringBuffer();
for (int i =0; i < a.length; i++) {
s.append(a[i]);
if (i != a.length - 1) {
s.append(",");
}
}
return s.toString();
}
/**
* @param args
*/
public static void main(String[] args) {
String[] a = {"北京", "上海", "杭州"};
System.out.println(convert(a));