$ 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