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/23-primitive-patterns.txt

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+$ java --enable-preview PrimitivePatterns     (JDK 27)
+--- instanceof <primitive>: an exact-conversion test, not a cast
+100 instanceof byte = true
+300 instanceof byte = false   (a byte holds -128..127)
+CHECK ok   : 100 converts to byte exactly, 300 does not
+binding: byte narrow = 100
+16_777_216 instanceof float = true
+16_777_217 instanceof float = false   (float has a 24-bit significand)
+CHECK ok   : int to float is exact up to 2^24 and lossy after
+--- switch on a long, with pattern labels and a guard
+classify(0) = zero
+classify(1) = one
+classify(-7) = negative (-7)
+classify(9000000000) = positive (9000000000)
+CHECK ok   : long switch dispatches on constants, then patterns
+--- switch on an Object: an Integer matches 'case int'
+describe(Integer 7) = an int 7
+describe(Integer 5000) = a large int 5000
+describe(Long 7) = a long 7
+describe(Double 2.5) = a double 2.5
+describe(String hello) = a String of length 5
+describe(Character x) = something else: x
+CHECK ok   : an Integer 5000 matches case int with a guard
+--- record pattern with a narrowing primitive component
+Reading[celsius=36] -> fits in a byte: 36
+Reading[celsius=4000] -> needs a full int: 4000
+CHECK ok   : Reading(byte c) matches 36 but not 4000
+exit=0