带逗号的java数字字符串

Question

我在解决此问题时遇到问题：

Write a structures program that can accept two integer numbers up to 40 digit and perform the following:

1. add the two numbers together and display the result
2. the result number should should be seperated by commas.

所以我可以使用BigInteger做第一件事，但是对于第二部分，我遇到了一些问题。我不知道应该如何在字符串中添加逗号，我使用了for循环来处理split，但它不起作用

我想起来了谢谢你的帮助

   public static String NewString (String num)
   {
    String sent = "" ;
    int count = 0;
        for ( int index = num.length()-1 ; index >= 0 ; index --)
        {
       count++;
           sent = num.charAt(index) + sent;
       if(count % 3 == 0 && index != 0) 
       sent = "," + sent;
        }
      return sent;
   }

Answer 1

你可以用

String formattedInteger = NumberFormat.getNumberInstance(Locale.US).format(bigInteger);

或者你也可以自己写。这将非常简单，只需将BigInteger转换为String，然后向后循环，每传递第三个字符添加一个逗号

Answer 2

以下代码：

• 将两个数字相加并显示结果
• 结果编号应以逗号分隔

这是不言自明的，希望这有帮助：）

package stackoverflow;

import java.math.BigInteger;

/**
 * Created by Nick on 11/13/14.
 *
 * Add two numbers together and display the result
 * The result number should be separated by commas.
 */
public class SO_26916958 {

private static BigInteger arg1;
private static BigInteger arg2;

public static void main(String[] args) {
    arg1 = new BigInteger (args[0].getBytes());
    arg2 = new BigInteger (args[1].getBytes());
    BigInteger sum = arg1.add(arg2);
    String bigIntegerString = sum.toString();

    String output = recursivelyAddComma(bigIntegerString);

    System.out.print(bigIntegerString +"\n");
    System.out.print(output);
}

private static String recursivelyAddComma (String s) {
    int length = s.length();
    StringBuilder output = null;

    if(length <= 3) {
        return s.toString();
    }

    return  recursivelyAddComma(s.substring(0, length - 3)).concat(",").concat(s.substring(length - 3, length));

    }

}