Question

BigInteger bx=new BigInteger("3806908688");

byte x[]=new byte[4];

String s=bx.toString(10);

System.out.println("string: "+s);

x=s.getBytes();

int l=0,i=0;

l |= x[i] & 0xFF;

l <<= 8;

l |= x[i+1] & 0xFF;

l <<= 8;

l |= x[i+2] & 0xFF;

l <<= 8;

l |= x[i+3] & 0xFF;

System.out.println(l);

The output is 859320374 instead of 3806908688. Why is this happening when I’m converting a BigInteger into a byte array and printing this byte array as an integer

I also tried using bx.toByteArray() but the result is same

Answer 1

If you have to do it manually, do it in a loop:

// Take care of negative values
long l = (bigInt.compareTo(BigInteger.ZERO) < 0) ? -1 : 0;
byte[] array = bigInt.toByteArray();
for(int i=0; i<array.length-1; i++) {
    l |= array[i] & 0xFF;
    l <<= 8;
}
l |= array[array.length-1] & 0xFF;

Alternatively you could just use methods offered by BigInteger:

int someInt = bigInt.intValue();
long someLong = bigInt.longValue();