Why does java.util.zip.CRC32.getValue() return a long, not an int?

Question

See the title. The returned value is 32 bits, right? Why not return an int?

Answer 1

Because if it returned an int, half of the CRC's would be negative. The expectation is that a 32-bit CRC is unsigned, i.e. 0..4294967295, which cannot be represented in an int.

Answer 2

java.util.zip.CRC32 implements the Checksum interface, which requires a long return type for getValue(), therefore requiring a long for a 32-bit checksum; the upper 32 bits of the output are almost definitely 0.