Fix sign extension in BitField.getValue for top-bit fields

[alhudz]

BitField.getValue(int) and getValue(long) read the field with getRawValue and then shift it down with an arithmetic >>. When the field sits on the top bit of the holder (bit 31 for the int overload, bit 63 for the long overload added in 3.21.0) the masked value is negative, so >> sign-extends and the field reads back negative. new BitField(0x8000000000000000L).getValue(0x8000000000000000L) gives -1 for a one-bit field whose value is 1, and new BitField(0xFF000000).getValue(0xFF000000) gives -1 from the int overload while getValue(long) returns 255 for the same field.

Use the unsigned >>> in both getters so the selected bits come down as magnitude. The value is reconstructed at the shift, so fixing it there also covers getShortValue/getByteValue, which delegate through getValue, and it leaves the mask handling from #1711 untouched. Fields that do not reach the top bit are unchanged because >> and >>> agree on a non-negative value.

[garydgregory]

Good find @alhudz , will merge, do you see other issues in the code base wit bit shifts?

[Copilot]

Pull request overview

Fixes incorrect sign extension when extracting bitfields that occupy the top bit(s) of an int (bit 31) or long (bit 63) in BitField.getValue(...), ensuring extracted values reflect the intended unsigned magnitude.

Changes:

• Switch BitField.getValue(int) to use unsigned right shift (>>>) to avoid sign extension for top-bit fields.
• Switch BitField.getValue(long) to use unsigned right shift (>>>) to avoid sign extension for top-bit fields.
• Add targeted regression tests covering top-bit and top-range masks for both int and long holders.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/main/java/org/apache/commons/lang3/BitField.java	Uses unsigned right shift in getValue overloads to prevent sign extension when the masked value is negative.
src/test/java/org/apache/commons/lang3/BitFieldTest.java	Adds regression tests validating correct extraction for fields at bit 31 and bit 63 (and high-range masks).

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