Trades.java class is incorrectly comparing ID strings

Trades.java contains the following:

@Override
public int compare(Trade trade1, Trade trade2) {
    return trade1.getId().compareTo(trade2.getId());
}

Since .getId() returns a String, comparing two Strings using compareTo is a lexicographical comparison, and would not work reliably, especially when the length of the String is different.

Consider this example:

public static void main(String[] args) {
  String id = "100";
  // check if the value is less than 100
  System.out.println(id.compareTo("99"));
  // check if value is equal to 100
  System.out.println(id.compareTo("100"));
  // check if value is greater than 100
  System.out.println(id.compareTo("101"));
}

Console:

-8
0
-1

"100".compareTo("99") returns a negative number which is lexicographically correct, but if these are trade Ids, then this is a bug.

We should therefore change the TradeIDComparator in Trades.java to convert the String into a BigInteger or Integer prior to the comparison.

something like this:

@Override
public int compare(Trade trade1, Trade trade2) {
	BigInteger id1 = new BigInteger(trade1.getId());
	BigInteger id2 = new BigInteger(trade2.getId());
	return id1.compareTo(id2);
}

[cymp]

@shimonm I addressed your problem in https://github.com/knowm/XChange/pull/2839, dealing with hexadecimal IDs as well.

private static final int[] ALLOWED_RADIXES = {10, 16};

@Override
public int compare(Trade trade1, Trade trade2) {
  for (int radix : ALLOWED_RADIXES) {
    try {
      BigInteger id1 = new BigInteger(trade1.getId(), radix);
      BigInteger id2 = new BigInteger(trade2.getId(), radix);
      return id1.compareTo(id2);
    } catch (NumberFormatException ignored) {
    }
  }
  return trade1.getId().compareTo(trade2.getId());
}

[shimonm]

Thank you! closing