Pass AST directly

I am implementing a tool that generates Java source code. It uses GJF to make the output more readable.

At the moment, source code is generated as text and written to memory, then it is parsed and formatted by GJF.

I was wondering whether you would support an API where a `JCCompilationUnit` or `JCTree` could be passed to GJF directly? That way, my tool could just generate a tree. There would be less overhead since writing and parsing could be skipped altogether.

首先閱讀 GJF 的公開格式化 API，以及目前將原始碼文字剖析為編譯單元的路徑。確定如何讓 JCCompilationUnit 或 JCTree 直接進入該路徑，同時不改變現有的格式化行為。當所要求的樹狀結構 API 已定義並實作，且有測試展示格式化輸出時，即視為完成。

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