Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
2026-09-21 15:08:50 +00:00
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+#!/usr/bin/env python3
+"""Diff two javap dumps produced by dump_api.py and report changes to PUBLIC API only.
+
+usage: apidiff.py <old-dump> <new-dump> [--vector-only]
+
+A class is reported only if its declaration starts with 'public' in the old or the new dump, so
+package-private implementation classes (which javap -public still lists) do not drown the signal.
+"""
+import collections
+import re
+import sys
+
+
+def parse(path):
+    classes = collections.OrderedDict()
+    decl = {}
+    cur = None
+    for line in open(path):
+        line = line.rstrip("\n")
+        if line.startswith("#####") or line.startswith("Compiled from") or not line.strip():
+            continue
+        if not line.startswith(" "):
+            m = re.search(r"(?:class|interface|enum|@interface|record)\s+([\w.$]+)", line)
+            cur = m.group(1) if m else line
+            classes[cur] = set()
+            decl[cur] = line
+        elif cur is not None and line.strip() != "}":
+            classes[cur].add(line.strip())
+    return classes, decl
+
+
+def is_public(decl_line):
+    return decl_line.startswith("public ") or decl_line.startswith("protected ")
+
+
+def main():
+    old, old_decl = parse(sys.argv[1])
+    new, new_decl = parse(sys.argv[2])
+    vector_only = "--vector-only" in sys.argv
+
+    def keep(name):
+        if vector_only and not name.startswith("jdk.incubator.vector."):
+            return False
+        if name.startswith("file") or "Error: Access Flags" in old_decl.get(name, "") + new_decl.get(name, ""):
+            return False
+        return is_public(old_decl.get(name, "")) or is_public(new_decl.get(name, ""))
+
+    print("## public classes removed")
+    for c in sorted(set(old) - set(new)):
+        if keep(c):
+            print("  " + c)
+    print("## public classes added")
+    for c in sorted(set(new) - set(old)):
+        if keep(c):
+            print("  " + c)
+    print("## public class changes")
+    for c in sorted(set(old) & set(new)):
+        if not keep(c):
+            continue
+        removed = old[c] - new[c]
+        added = new[c] - old[c]
+        d_old, d_new = old_decl[c], new_decl[c]
+        if removed or added or d_old != d_new:
+            print(c)
+            if d_old != d_new:
+                print("   - " + d_old.strip())
+                print("   + " + d_new.strip())
+            for x in sorted(removed):
+                print("   - " + x)
+            for x in sorted(added):
+                print("   + " + x)
+
+
+main()