numeric parameter conversion should parse as decimal

[remkop]

Currently:
Byte, short, int and long conversion (for both primitives and wrappers) uses the decode method, so numbers starting with 0x, 0X or # are interpreted as hexadecimal numbers, numbers starting with 0 are interpreted as octal numbers, and otherwise the number is interpreted as a decimal number.

But see POSIX Utility Conventions Requirement 6:

Unless otherwise specified, whenever an operand or option-argument is, or contains, a numeric value:
The number is interpreted as a decimal integer.

Perhaps using the decode method by default is not a good idea.
Let's revert to the parse methods that interpret as a decimal value, and in the documentation suggest that applications that want to support hex values register the decode method:

commandLine.registerConverter(Integer.class, s -> Integer::decode);