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

docs/output/22-lazy.txt

@@ -0,0 +1,22 @@
+$ java --enable-preview LazyDemo     (JDK 27)
+--- a lazy constant computes once, on first use
+toString before first get(): jdk.internal.lang.LazyConstantImpl@...[computing function=LazyDemo$$Lambda/0x...@...]
+  (loading settings on main)
+toString after  first get(): jdk.internal.lang.LazyConstantImpl@...[Settings[region=ap-south-1, poolSize=16]]
+CHECK ok   : get() returns the same instance every time
+CHECK ok   : the supplier ran exactly once
+--- and once even when 64 threads race for it
+CHECK ok   : 64 racing threads triggered exactly one initialisation
+--- List.ofLazy: each element is computed on first access
+computed so far: 0
+squares.get(3) = square(3)=9
+squares.get(3) = square(3)=9   (second read)
+CHECK ok   : only element 3 was ever computed
+--- Map.ofLazy: the keys are fixed, the values are computed on first access
+lengths.get("gamma") = 5
+CHECK ok   : only the requested key's value was computed
+--- Set.ofLazy (new in 27): membership is decided by a predicate, on demand
+primes.contains(7) = true, primes.contains(6) = false
+CHECK ok   : the lazy set answers membership using the predicate
+primes = [2, 3, 5, 7]
+exit=0