RFR: 8296734: JarVerifier:: mapSignersToCodeSource should cache in map

[pandaapo]

On Thu, 10 Nov 2022 21:08:34 GMT, Sean Mullan <mullan at openjdk.org> wrote:

> If you want to instead do some general cleanup in this class for JDK 20, you could instead remove this method and several other unused methods from `JarVerifier`.

Before I began to make general cleanup, I looked up from this unused method `JarVerifier#mapSignersToCodeSource()`and found all related call stacks:
![未命名文件](https://user-images.githubusercontent.com/35672972/201353836-9151ddfa-10c5-4ecc-96f8-f8aa0c7e2798.png)
Can I remove these methods in `JarFile`, `JavaUtilJarAccess` and its only implementation `JavaUtilJarAccessImpl`?

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PR: https://git.openjdk.org/jdk/pull/11072