Here you can find the source of add(String number1, String number2)
public static String add(String number1, String number2)
//package com.java2s; //License from project: Apache License import java.math.BigDecimal; public class Main { public static String add(String number1, String number2) { BigDecimal bd = new BigDecimal(number1); return bd.add(new BigDecimal(number2)).toString(); }/*from w w w .ja v a 2 s.c om*/ }