So java has a long type suffix for literals: (123L), a double type suffix (43.21D), a floating point suffix (1.234F). So ... why no byte type suffix? For example, when writing some testing code you MUST cast all your bytes when they are used as function parameters.
ByteBuffer b = ByteBuffer.allocate(100);
b.put((byte)3); // super annoying
b.put(3b); // if only
It is clear that using B or b would not work since it would conflict with the ability to specify a byte in hexadecimal or octal (a critical language feature). But some other letter, like Z z? or Y y (for bYte)?