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

other-changes/src/Api27.java

@@ -0,0 +1,42 @@
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.nio.charset.StandardCharsets;
+import java.security.KeyStore;
+import java.time.Instant;
+import java.util.Set;
+import javax.crypto.spec.SecretKeySpec;
+
+/**
+ * Small additions to the JDK 27 public API found by diffing javap dumps of 26 and 27
+ * (docs/output/51-api-diff-26-to-27.txt), each exercised once. Compile with --release 27.
+ */
+public class Api27 {
+    public static void main(String[] args) throws Exception {
+        System.out.printf("Math.acosh(2)  = %.6f%n", Math.acosh(2));
+        System.out.printf("Math.asinh(1)  = %.6f%n", Math.asinh(1));
+        System.out.printf("Math.atanh(.5) = %.6f%n", Math.atanh(0.5));
+        Check.that(Math.abs(Math.acosh(Math.cosh(1.5)) - 1.5) < 1e-12, "acosh inverts cosh");
+
+        String s = "na\u00efve caf\u00e9";
+        int utf8 = s.encodedLength(StandardCharsets.UTF_8);
+        System.out.println("\"" + s + "\".length() = " + s.length() + ", encodedLength(UTF_8) = " + utf8);
+        Check.that(utf8 == s.getBytes(StandardCharsets.UTF_8).length, "encodedLength matches getBytes().length without allocating the array");
+
+        BigDecimal cube = new BigDecimal("27").rootn(3, MathContext.DECIMAL64);
+        System.out.println("BigDecimal(27).rootn(3) = " + cube);
+        Check.that(cube.compareTo(new BigDecimal("3")) == 0, "rootn(3) of 27 is 3");
+
+        KeyStore ks = KeyStore.getInstance("PKCS12");
+        ks.load(null, null);
+        char[] pw = "changeit".toCharArray();
+        ks.setEntry("aes-key", new KeyStore.SecretKeyEntry(new SecretKeySpec(new byte[16], "AES")),
+                new KeyStore.PasswordProtection(pw));
+        Instant created = ks.getCreationInstant("aes-key");
+        System.out.println("KeyStore.getCreationInstant(\"aes-key\") returns an Instant: " + (created != null));
+        Check.that(created != null && Math.abs(created.toEpochMilli() - System.currentTimeMillis()) < 60_000,
+                "KeyStore.getCreationInstant returns the entry's creation time as a java.time.Instant");
+
+        Set<Integer> evens = Set.ofLazy(Set.of(1, 2, 3, 4), n -> n % 2 == 0);
+        Check.that(evens.contains(2) && !evens.contains(3), "Set.ofLazy(Set, Predicate) exists (preview API)");
+    }
+}

other-changes/src/Check.java

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+/**
+ * Tiny assertion helper so every demo is self-checking: a claim that stops being true turns the
+ * run red instead of quietly printing something different. Passing checks are echoed, so the
+ * transcript shows exactly what was verified.
+ */
+final class Check {
+    private Check() {}
+
+    static void that(boolean condition, String claim) {
+        if (!condition) {
+            throw new AssertionError("CHECK FAILED: " + claim);
+        }
+        System.out.println("CHECK ok   : " + claim);
+    }
+}

other-changes/src/Compat.java

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+import java.util.Locale;
+
+/**
+ * A behaviour change from the JDK 27 release notes (JDK-8355522) that needs no new API to trigger, so the
+ * same class file can run on 26 and 27 and show the difference. Run by scripts/other-changes.sh.
+ */
+public class Compat {
+    public static void main(String[] args) {
+        System.out.println("java.version           = " + System.getProperty("java.version"));
+        System.out.println("Locale(\"iw\").language  = " + Locale.forLanguageTag("iw").getLanguage()
+                + "   (Hebrew; old code 'iw', current code 'he')");
+    }
+}

other-changes/src/SpawnProbe.java

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+/** Starts one child process. JDK 27 removed the VFORK launch mechanism, so a script that pinned it now fails here. */
+public class SpawnProbe {
+    public static void main(String[] args) throws Exception {
+        Process p = new ProcessBuilder("true").start();
+        System.out.println("child exited with " + p.waitFor());
+    }
+}