拼接字符串时去掉最后一个多余逗号

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));
}

StringBuilder sdb = new StringBuilder();
for ( int t = 0; t < memberLen; t++ )
{
    memTemp = stafferMap.get( strMember[t] );
    if ( memTemp != null )
    {
        if ( sbd.length > 0 )
        {
            sbd.append( "," ).append( memTemp );
        }else{
            sbd.append( memTemp );
        }
    }
}