javademos/migration-17-25

migration-17-25

Companion module for the ankurm.com post Java 17 to Java 25 Migration Guide: The Direct Jump.

The probes in src/probes/ are compiled once with JDK 17 (--release 17) and run unchanged on JDK 17.0.20.1 and JDK 25.0.4.1, which is what a team skipping 21 actually does. src/removed/ holds four tiny sources that use APIs removed or newly deprecated between 17 and 25; they are compiled with both JDKs.

export JDK17=/path/to/jdk-17 JDK25=/path/to/jdk-25
./scripts/run-all.sh      # regenerates output/

Output	Shows
01-runtime-behaviour.txt	Security Manager, Thread.stop, default charset, finalize, Unsafe on both runtimes
02-startup-flags.txt	Which 17-era JVM options still start on 25
03-compile-removed-apis.txt	What javac says about four APIs on each JDK
04-jdeps-jdeprscan.txt	The scanners run with JDK 25 tools against the JDK 17-built jar
05-gc-defaults.txt	Default collector and heap ergonomics with no flags
06-legacy-stack-on-25.txt	mvn test on JDK 25 for four generations of one Spring app (from spring-boot-demo/openrewrite)
07-framework-minimums.txt	Vendor documentation quotes (not produced by running code)