Java拼接字符串时,去掉最后一个多余的逗号

String str[] = { "hello", "beijing", "world", "shenzhen" };
StringBuffer buf = new StringBuffer();

for (int i = 0; i < str.length; i++) {
buf.append(str[i]).append(",");
}

if (buf.length() > 0) {
//方法一  : substring
System.out.println(buf.substring(0, buf.length()-1));
//方法二 ：replace
System.out.println(buf.replace(buf.length() - 1, buf.length(), ""));
//方法三： deleteCharAt
System.out.println(buf.deleteCharAt(buf.length()-1));
}