Groovy vs Java – Subtle difference in Hex Literals

Recently I stumbled across a small but annoying difference in border cases of hex literals between Groovy and Java

In Groovy, this

println(0xff000000.class)

will yield class java.lang.Long

In Java, this

Object x = 0xff000000;
System.out.println(x.getClass());

will yield java.lang.Integer

In Groovy, the literal is a long because it’s too big to fit into an Integer (that’s true, 4278190080 is well above 2^31 and thus a Long), but in Java it’s -16777216, which is an Integer.
The solution is to suffix the constant with an I, e.g. 0xff000000I, then Groovy leaves it as an Integer (Java doesn’t support that notation, though).

This is relevant when doing bit operations, e.g. the expression

(-1 & 0xff000000) >> 24

is 255 in Groovy, and -1 in Java

Thank goodness you don’t need bit twiddling too much this days …