Summary

AccessFlag.maskToAccessFlags should be able to reject access flags not present in a particular location in a particular version, and the accessFlags() methods for classes, methods, constructors, and fields should reflect the access flags specified for the class file format version of the original class file.

Problem

The accessFlags() methods added in JDK 20 to java.lang.Class, java.lang.reflect.Executable, and java.lang.reflect.Field are silent about the dependency of the access flags on the class file format version. For current and past class file format versions there are few significant variations but future changes are anticipated that change the meaning of some access flag mask bits. One example is the strictfp/ACC_STRICT access flag that only applies to releases 2 through 16.

Solution

The accessFlags() methods should mention that the access flags returned are those applicable to the class file format version of the class. The existing AccessFlag.Locations API already contains information about the locations that are applicable to a class file format version. That information should be used to construct the set of AccessFlags returned. A method is added to AccessFlag that returns the applicable flags for a particular mask, Location, and class file format version:

Set<AccessFlags> maskToAccessFlags(int mask, Location, ClassFileFormatVersion)

Specification

java.lang.reflect.AccessFlag now has two maskToAccessFlags methods:

/**
 * {@return an unmodifiable set of access flags for the given mask value
 * appropriate for the location in the current class file format version}
 *
 * @param mask bit mask of access flags
 * @param location context to interpret mask value
 * @throws IllegalArgumentException if the mask contains bit
 * positions not defined for the location in the current class file format
 * @throws NullPointerException if {@code location} is {@code null}
 */
public static Set<AccessFlag> maskToAccessFlags(int mask, Location location) {

/**
 * {@return an unmodifiable set of access flags for the given mask value
 * appropriate for the location in the given class file format version}
 *
 * @param mask bit mask of access flags
 * @param location context to interpret mask value
 * @param cffv the class file format to interpret mask value
 * @throws IllegalArgumentException if the mask contains bit
 * positions not defined for the location in the given class file format
 * @throws NullPointerException if {@code location} or {@code cffv} is {@code null}
 * @since 25
 */
public static Set<AccessFlag> maskToAccessFlags(int mask, Location location, ClassFileFormatVersion cffv) {

For the existing 2-arg version, return tag adds "in the current class file format version", "position not supported" becomes "positions not defined", and a missing clause for NPE is added.