含.java文件的Jar包用法、编译器异常及两类Jar包差异问询

Great question—let’s break this down clearly, especially since you’ve already seen firsthand how swapping JAR types fixes a tricky Xposed error.

Core Differences Between .class and .java JARs #

• .class JARs: These hold compiled Java bytecode—the low-level format the JVM executes directly. They’re the standard way to distribute Java libraries: compact, optimized, and ready to run. Some JARs include .java files for documentation, but they’re not required for execution.
• .java JARs: These contain uncompiled raw Java source code. They can’t be run directly by the JVM; instead, they need to be compiled first (either manually or by a tool like a build system or framework that handles dynamic compilation).

Why .java Files in a JAR Fixed Your Xposed IllegalAccessError #

Your hunch about them acting like an "interface" to avoid access issues is spot-on—here’s the exact reason this worked for Xposed:

• When you use a .class JAR for hooking, Xposed is working with pre-compiled bytecode that has strict access modifiers (like private, protected, or package-private) already locked in. The JVM enforces these access rules at runtime, so if your hook tries to access a restricted member, it throws an IllegalAccessError.
• Swapping to a .java JAR gives Xposed more flexibility. The framework can dynamically compile the source code on-the-fly, and during that compilation step, it uses its bytecode manipulation tools to modify access modifiers—effectively lifting those restrictions so your hook can access the necessary members without triggering the error.

In short: .class files are a "final" version of the code that’s hard to tweak after compilation, while .java files are a blueprint Xposed can rewrite and recompile to fit its hooking needs.

内容的提问来源于stack exchange，提问作者Hyeonseo Yang