Implement appendTail and appendReplacement methods in Matcher

[Jitmisra]

#589

Summary

Implements the two missing appendTail() and appendReplacement() methods in JPF's Matcher model class. These were marked as TODO in the codebase.

Problem

Programs using the standard Java regex find-and-replace pattern could not be verified by JPF:

while (m.find()) {
    m.appendReplacement(sb, "replacement");
}
m.appendTail(sb);

Calling these methods would fail because they weren't implemented.

Solution

Files Changed:

File	Description
src/classes/.../java/util/regex/Matcher.java	Added native method declarations with Javadoc
src/peers/.../JPF_java_util_regex_Matcher.java	Implemented native peer methods
src/tests/.../regex/MatcherAppendTest.java	Added 5 unit tests

Implementation Details

The tricky part was handling Java 11+ compact strings. Unlike Java 8 where StringBuffer uses char[], Java 11+ uses:

• byte[] for storage (compact representation)
• coder field: 0 = LATIN1, 1 = UTF16

The implementation:

1. Delegates to the real host JVM Matcher.appendReplacement/appendTail
2. Converts the result back to JPF's StringBuffer format
3. Handles encoding upgrades (LATIN1 → UTF16) when needed

Tests Added

• testAppendReplacementAndTail - Multiple replacements
• testAppendReplacementSingleMatch - Single match
• testAppendTailNoMatch - No matches scenario
• testAppendReplacementWithGroupReference - Using $1 groups
• testAppendReplacementEmptyString - Empty replacement

Verification

./gradlew test
BUILD SUCCESSFUL
parallelTest: 1019 passed, 0 failed
singleThreadTest: 16 passed, 0 failed