[Q#3028380][A#3028429] How to convert BigInteger to String in java

https://stackoverflow.com/q/3028380

I converted a String to BigInteger as follows: Now I want my string back. I'm using m.toString() but that's giving me the desired result. Why? Where is the bug and what can I do about it?

Answer

https://stackoverflow.com/a/3028429

You want to use BigInteger.toByteArray() The way I understand it is that you're doing the following transformations: And you want the reverse: Note that you probably want to use overloads of String.getBytes() and String(byte[]) that specifies an explicit encoding, otherwise you may run into encoding issues.

APIzation

String msg = "Hello there!";
BigInteger bi = new BigInteger(msg.getBytes());
System.out.println(new String(bi.toByteArray())); // prints "Hello there!"
String  -----------------> byte[] ------------------> BigInteger
          String.getBytes()         BigInteger(byte[])
BigInteger ------------------------> byte[] ------------------> String
             BigInteger.toByteArray()          String(byte[])

package com.stackoverflow.api;

import java.math.BigInteger;
import java.util.Scanner;

public class Human3028429 {

  public static String convertStringToBigInteger() {
    Scanner sc = new Scanner(System.in);
    System.out.println("enter the message");
    String msg = sc.next();
    BigInteger bi = new BigInteger(msg.getBytes());
    return new String(bi.toByteArray());
  }
}

package com.stackoverflow.api;

import java.math.BigInteger;

/**
 * How to convert BigInteger to String in java
 *
 * @author APIzator
 * @see <a href="https://stackoverflow.com/a/3028429">https://stackoverflow.com/a/3028429</a>
 */
public class APIzator3028429 {

  public static String convertBiginteger(String msg) throws Exception {
    BigInteger bi = new BigInteger(msg.getBytes());
    return new String(bi.toByteArray());
  }
}