Add Support for Lambda, Comments, Generics, and For-Each to Java Grammar

[pdfCN]

This PR significantly enhances the Java grammar by adding support for essential language features that were previously missing:

✅ Added Features:

• Lambda expressions: (a, b) -> a + b
• Java comments: // line and /* block */
• Generics: List<String>, Map<K, ? extends V>, Set<?>, etc.
• For-each loops: for (int i : list)

📊 Evaluation:

• Model: Qwen/Qwen2.5-Coder-1.5B (Greedy)
• Benchmark: HumanEval-x (Java version)

Version	Pass@1
wo/ syncode (Original Model)	42.7%
w/ syncode (Original Parser)	28.0%
w/ syncode (Update parser)	45.7%

🔍 Notes:

This improvement addresses key syntax limitations in the original grammar, enabling more accurate code generation and parsing for Java. It directly contributes to better performance on HumanEval-x and closes gaps in practical code scenarios.

[shubhamugare]

Perfect! Thanks for the PR