Upgrade Java version to 25 on iteration 3

[moonct]

Java Version Upgrade — Executive Report

Project: Bytecode Viewer 2.13.2 | Date: 2026-05-11 | Target: Java 25

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1. 📋 Executive Summary

Bytecode Viewer, an open-source Java/Android reverse engineering suite, was successfully upgraded from Java 8 to Java 25 using an automated OpenRewrite migration pipeline combined with AI-assisted compilation fix-up via Amazon Kiro CLI. The automated tooling handled the bulk of the migration across 80+ source files in under 4 minutes. A post-migration compilation failure caused by unresolved OpenRewrite template placeholders was identified and fully resolved by Kiro, resulting in a clean build with zero compilation errors and all tests passing.

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2. 🗂️ Application Changes

• Application: Bytecode Viewer — a Swing-based desktop Java reverse engineering tool
• Version: 2.13.2
• Source files modified: 80+ Java source files across the full codebase
• Build system: Maven (pom.xml updated to target Java 25)
• Scope: Full codebase migration spanning GUI, decompilers, plugins, CLI, utilities, and resource handling layers

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3. 🛠️ Tools Used

Tool	Role
☕ Java SDK 25	Target runtime and compiler
🔁 OpenRewrite 6.39.0	Automated source code migration recipe engine
📦 com.amazonaws.java.migrate.UpgradeToJava25	AWS-provided composite recipe orchestrating the full Java 8→25 upgrade path
🤖 Amazon Kiro CLI 2.0.1	AI agent used to diagnose and fix post-migration compilation errors
🏗️ Apache Maven 3.x	Build, compile, test, and package

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4. 🔧 Code Changes

Automated by OpenRewrite

• ✅ pom.xml — Java version properties and maven-compiler-plugin updated to release 25
• ✅ instanceof pattern matching — if (x instanceof Foo) { Foo f = (Foo) x; } → if (x instanceof Foo f) across 15+ files (FileDrop, FieldCallSearch, MethodCallSearch, LDCSearch, ArrayParser, MethodCallParser, ConditionalParser, MyVoidVisitor, FieldAccessParser, ParserUtil, ClassViewer, TabComponent, GoToAction, ExtendedJOptionPane, ASMResourceUtil, and more)
• ✅ Switch expressions — Traditional switch statements converted to switch expressions (HexViewer, InstructionPrinter, BytecodeViewPanelUpdater, ClassViewer)
• ✅ String.formatted() — String.format(...) → "...".formatted(...) (FileHeaderUtils, MalwareCodeScanner, StackFramesRemover, PluginManager)
• ✅ Text blocks — Multi-line string concatenations converted to """...""" (APKExport, JavaBytecodeTokenMaker, ClassViewer)
• ✅ URL constructor → URI.create() — Deprecated new URL(...) replaced with URI.create(...).toURL() (PingBack, Boot, UpdateCheck)
• ✅ Paths.get() → Path.of() — (JRTExtractor, DirectoryResourceImporter)
• ✅ SequencedCollection APIs — list.get(0) → list.getFirst(), list.get(list.size()-1) → list.getLast() (MiscUtils, JRTExtractor, Settings, APKExport, ClassNodeDecompiler, MethodNodeDecompiler, FieldNodeDecompiler, MainViewerGUI, ResourceListIconRenderer, MyErrorStripe, GoToAction)
• ✅ Unused variable _ — Unused lambda/catch parameters renamed to _ across 30+ files
• ✅ @Serial annotation — Added to serialVersionUID fields in Swing components
• ✅ System.out → IO.println() — In applicable contexts across CLI and utility classes
• ✅ Instance main method — public static void main(String[] args) modernized in BytecodeViewer and IconDemo
• ✅ ClassLoader.defineClass — Migrated deprecated API in LibraryClassLoader
• ✅ Extra semicolons removed — (BootState, CLIAction, ContextMenuType, DecompilerViewComponent, New, GoToBinaryPositionMode)

Manual fixes by Kiro CLI (post-OpenRewrite)

• 🔨 InstructionPrinter.java — OpenRewrite left 16 broken __P__.<String>p() placeholders in a pattern-matching switch. Restored the original if-instanceof dispatch chain calling printVarInsnNode(), printIntInsnNode(), etc.
• 🔨 AllatoriStringDecrypter.java — OpenRewrite replaced a complex 70-line if-instanceof block with broken placeholders. Fully restored the Allatori string decryption logic (LDC tracking, invokestatic detection, class loading, and InvokeDynamic handling).
• 🔨 BytecodeViewPanelUpdater.java (×2) — yield __P__.nullp() placeholder in switch expression default branches replaced with yield null.
• 🔨 ClassViewer.java (×1) — Same yield __P__.nullp() placeholder replaced with yield null.

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5. ⏱️ Time Savings Estimate

Activity	Manual Estimate	Automated/AI
Reviewing and updating 80+ files for Java 25 idioms	~12–16 hours	~4 min (OpenRewrite)
Diagnosing broken placeholder syntax across 4 files	~1–2 hours	~5 min (Kiro CLI)
Restoring complex AllatoriStringDecrypter logic	~1 hour	~2 min (Kiro CLI)
Build verification and test runs	~30 min	~2 min (automated)
Total estimated savings	~15–20 hours	~13 min total

OpenRewrite itself estimated 12h 15m saved (logged in the build output). Kiro's fix-up work adds an additional ~2–3 hours of manual debugging avoided.

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6. 🚀 Next Steps

Validation

• 🧪 Run the full test suite in a CI environment with JDK 25 to catch any runtime regressions
• 🖥️ Perform manual smoke testing of the GUI — load a JAR/APK, verify all 6 decompilers render output correctly
• 🔍 Verify the Allatori String Decrypter plugin executes correctly end-to-end (the restored logic was complex)
• 📦 Validate the packaged JAR launches correctly with java -jar on JDK 25

Improvement Recommendations

• ⚠️ OpenRewrite placeholder bug — Report the __P__.<T>p() / __P__.nullp() unresolved template issue to the OpenRewrite project; these indicate the IfElseIfConstructToSwitch + SwitchCaseReturnsToSwitchExpression recipe chain fails silently on complex method bodies
• 🔒 Pin the com.amazonaws.java.migrate.UpgradeToJava25 recipe version in rewrite.yml to ensure reproducible future runs
• 🧹 Consider enabling --enable-preview in the Maven compiler config to access Java 25 preview features (value types, etc.) if needed in future iterations
• 📊 Add a baseline set of unit tests for the decompiler output to catch regressions in future upgrades
• 🔄 Schedule periodic OpenRewrite runs (e.g., quarterly) to keep the codebase current with new Java LTS idioms