Concurent calls to `ClassLoader.definePackage()` can yield `IllegalArgumentException`s if the package is already defined. Some built-in class loaders, like `URLClassLoader`, already handle this case, but custom class loaders (would) have to handle this case.
This change updates the logic of `CL.definePackage` to not throw an IAE if the "redefined" package is equal to the already defined one. Tests added in `jdk/java/lang/Package/PackageDefineTest.java` (+ pulling up the `TestClassLoader` from `PackageDefineTest`). ------------- Commit messages: - spec (javadoc) - move checks to CL + hoist IAE checks from URL/BuiltinClassLoaders - 8349545: ClassLoader.definePackage() throws IllegalArgumentException if package already defined Changes: https://git.openjdk.org/jdk/pull/23737/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23737&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8349545 Stats: 260 lines in 6 files changed: 218 ins; 29 del; 13 mod Patch: https://git.openjdk.org/jdk/pull/23737.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/23737/head:pull/23737 PR: https://git.openjdk.org/jdk/pull/23737
