Java 如何使用正则表达式去除前导0

String s="0000000002121210"
s=s.replaceAll("^(0+)", "");
System.out.println(s);

public static String insertComma(String s, int len) {
    if (s == null || s.length() < 1) {
        return "";
    }
    NumberFormat formater = null;
    double num = Double.parseDouble(s);
    if (len == 0) {
        formater = new DecimalFormat("###,###");
 
    } else {
        StringBuffer buff = new StringBuffer();
        buff.append("###,###.");
        for (int i = 0; i < len; i++) {
            buff.append("#");
        }
        formater = new DecimalFormat(buff.toString());
    }
    return formater.format(num);
}

double num = 5.5500; 
DecimalFormat decimalFormat = new DecimalFormat("##########.##########"); 
String numConverted = decimalFormat.format(num); //5.55