How to convert BigInteger to String in java

Question

I converted a String to BigInteger as follows:

Scanner sc=new Scanner(System.in); System.out.println("enter the message"); String msg=sc.next(); byte[] bytemsg=msg.getBytes(); BigInteger m=new BigInteger(bytemsg);  

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 1

You want to use BigInteger.toByteArray()

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

The way I understand it is that you're doing the following transformations:

  String  -----------------> byte[] ------------------> BigInteger           String.getBytes()         BigInteger(byte[]) 

And you want the reverse:

  BigInteger ------------------------> byte[] ------------------> String              BigInteger.toByteArray()          String(byte[]) 

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.

Answer 2

Use m.toString() or String.valueOf(m). String.valueOf uses toString() but is null safe.