两个超大的数相加

两个超大的数相加，当数的取值范围已经远远超过long型，可以将他们转化为字符串再相加，代码如下，用到了org.apache.commons.lang3.StringUtils类

import org.apache.commons.lang3.StringUtils;

public class BigNumberPlus {

public static String bigNumberPlus(String a,String b) {
int lenA = a.length();
int lenB = b.length();

if(lenA > lenB) {
b = StringUtils.leftPad(b,lenA,"0");
} else {
a = StringUtils.leftPad(a,lenB,"0");
}

int[] arrC = new int[a.length()+1];
for(int i=a.length()-1;i>=0;i--) {
int ai = Integer.parseInt(a.charAt(i)+"");
int bi = Integer.parseInt(b.charAt(i)+"");
int ci = arrC[i+1];
int t = ai+bi+ci;
arrC[i+1]=t%10;
arrC[i]=t/10;
}

StringBuffer str = new StringBuffer();
for(int i=0;i<arrC.length;i++) {
if(i==0 && arrC[i]==0) continue;
str.append(arrC[i]);
}

return str.toString();
}
public static void main(String[] args) {
String a = "985615478956321457896555214456358455617788885662489211024520211583312";
String b = "1574412369854631147823596334458552152385852121256121189655521445635845561077";
System.out.println(bigNumberPlus(a,b));
}
}