Update to Java 25 toolchain while targeting Java 8 bytecode

[Copilot]

Plan: Update Java toolchain to 25 while targeting Java 8

• Explore repository structure and understand current configuration
• Verify current build system (Gradle) and Java versions
• Identify files to modify
• Update build.gradle to use Java 25 toolchain
• Add sourceCompatibility and targetCompatibility for Java 8
• Update JUnit Jupiter version from 6.0.0 to 5.10.3 (last version supporting Java 8)
• Update README.md to reflect Java 25 requirement
• Build and test the changes
• Verify compiled bytecode targets Java 8 (major version 52)
• Remove redundant sourceCompatibility and targetCompatibility (options.release.set(8) already handles this)

Summary of Changes

1. app/build.gradle:

   • Changed toolchain from Java 21 to Java 25
   • Removed redundant sourceCompatibility and targetCompatibility settings (the options.release.set(8) already handles this)
   • Downgraded JUnit Jupiter from 6.0.0 to 5.10.3 (required for Java 8 compatibility)

2. README.md:

   • Updated documentation from "Java 21 is required!" to "Java 25 is required!"

Verification

✅ Build successful with Java 25 toolchain
✅ Compiled bytecode verified as major version 52 (Java 8)
✅ Application runs on Java 8 runtime
✅ All tests pass
✅ The --release 8 flag handles both source/target compatibility and API validation

Original prompt

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This section details on the original issue you should resolve

<issue_title>Java 25</issue_title>
<issue_description>develop with jdk 25, but still target java 8</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #24

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[Project516]

@copilot is this needed?

[Copilot]

You're right - they're not needed. The options.release.set(8) already handles both source and target compatibility (and does more by ensuring only Java 8 APIs are used). Removed in 4f4c7d5.

[Project516]

@copilot look at #24 (comment)