Summary

Move constants rarely used in a regular user processing routine out of java.lang.classfile.ClassFile.

Problem

ClassFile is currently the home of all class file constants, no matter where these constants appear. As such, it includes rarely used constants like AEV or CRT (which is not even in JVMS), or constants already modeled by other constructs, such as opcode or verification types.

These constants overwhelm new users, and hide the actually commonly-used constants (access flags and class file magic and versions). In addition, the name clash between Opcode enum constants and ClassFile opcode value constants means Opcode cannot be static imported if ClassFile is; this nuisance often happens in user class writing code.

ClassFile.DEFAULT_CLASS_FLAGS is an implementation detail. Its current value might not be suitable after integration of valhalla. We should hide it to avoid accidental impression that this value will stay the same forever.

In addition, some constants are values, and other constants are bit masks that are supposed to be combined with other masks but are not clarified to be so.

The SimpleVerificationTypeInfo enum constants with ITEM_ prefixes are now not as convenient as VT_ constants after they are moved to VerificationTypeInfo; we wish users to use the enum instead of the raw VT_ constants after the move.

Solution

These constants are moved elsewhere, usually as close as possible to the APIs that return these values. For example, the AEV values are now right by AnnotationValue.tag() that returns these values. Rename the constants to their local context after their move; i.e. to replace the generic AEV CRT prefixes with TAG or FLAG.

Remove the raw opcode constants. They are still accessible via Opcode::bytecode, and we can add back if there's need.

Remove ClassFile.DEFAULT_CLASS_FLAGS and keep it internal. Remove the constant pool tag for "unicode".

For bit mask constants (CRT and ACC), clarify they are bit masks.

Remove ITEM_ prefix for SimpleVerificationTypeInfo items. In particular, ITEM_ prefix was referring to the constant numbers instead of the verification types in https://docs.oracle.com/javase/specs/jvms/se22/html/jvms-4.html#jvms-4.7.4.

Specification

See attachment.