Add patterns module: pattern matching from JDK 21 to 27

Type, record and primitive patterns, guards, sealed exhaustiveness, MatchException via separate compilation, and eight captured transcripts. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a
2026-09-24 11:50:40 +00:00
parent 96b25c8fc4
commit bc91b9c8d0
36 changed files with 736 additions and 0 deletions
@@ -0,0 +1,87 @@
+$ javac preview/PrimitiveInstanceof.java     (25.0.4.1+1-LTS)
+preview/PrimitiveInstanceof.java:3: error: primitive patterns are a preview feature and are disabled by default.
+        if (i instanceof byte b) return i + " fits in a byte: " + b;
+            ^
+  (use --enable-preview to enable primitive patterns)
+1 error
+
+$ javac preview/PrimitiveInstanceof.java     (27+35)
+preview/PrimitiveInstanceof.java:3: error: primitive patterns are a preview feature and are disabled by default.
+        if (i instanceof byte b) return i + " fits in a byte: " + b;
+            ^
+  (use --enable-preview to enable primitive patterns)
+1 error
+
+$ javac --enable-preview --release 25 preview/PrimitiveInstanceof.java && java --enable-preview PrimitiveInstanceof     (25.0.4.1+1-LTS)
+100 fits in a byte: 100
+1000 fits in a short: 1000
+100000 needs an int
+0.5 converts to float 0.5 without loss
+0.1 does NOT convert to float without loss
+
+$ javac --enable-preview --release 27 preview/PrimitiveInstanceof.java && java --enable-preview PrimitiveInstanceof     (27+35)
+100 fits in a byte: 100
+1000 fits in a short: 1000
+100000 needs an int
+0.5 converts to float 0.5 without loss
+0.1 does NOT convert to float without loss
+
+$ javac --enable-preview --release 25 preview/PrimitiveSwitch.java && java --enable-preview PrimitiveSwitch     (25.0.4.1+1-LTS)
+OK | other success 204 | client error 404 | something else 500
+yes no
+zero one many (9223372036854775807)
+
+$ javac --enable-preview --release 27 preview/PrimitiveSwitch.java && java --enable-preview PrimitiveSwitch     (27+35)
+OK | other success 204 | client error 404 | something else 500
+yes no
+zero one many (9223372036854775807)
+
+$ javac --enable-preview --release 25 preview/PrimitiveInRecord.java && java --enable-preview PrimitiveInRecord     (25.0.4.1+1-LTS)
+whole degrees: 21
+fractional: 21.5
+not a reading
+
+$ javac --enable-preview --release 27 preview/PrimitiveInRecord.java && java --enable-preview PrimitiveInRecord     (27+35)
+whole degrees: 21
+fractional: 21.5
+not a reading
+
+$ javac --enable-preview --release 25 preview/PrimitiveEdges.java && java --enable-preview PrimitiveEdges     (25.0.4.1+1-LTS)
+0.0          int? true  float? true 
+-0.0         int? false float? true 
+NaN          int? false float? true 
+1.6777217E7  int? true  float? false
+1.0E10       int? false float? true 
+3.0          int? true  float? true 
+1099511627776 instanceof int? false
+Object holding Integer matches int pattern: 42
+Short in Object does not match int
+65 as char: A
+
+$ javac --enable-preview --release 27 preview/PrimitiveEdges.java && java --enable-preview PrimitiveEdges     (27+35)
+0.0          int? true  float? true 
+-0.0         int? false float? true 
+NaN          int? false float? true 
+1.6777217E7  int? true  float? false
+1.0E10       int? false float? true 
+3.0          int? true  float? true 
+1099511627776 instanceof int? false
+Object holding Integer matches int pattern: 42
+Short in Object does not match int
+65 as char: A
+
+$ javac --enable-preview --release 25 preview/BoxedToNarrower.java && java --enable-preview BoxedToNarrower     (25.0.4.1+1-LTS)
+preview/BoxedToNarrower.java:4: error: incompatible types: Integer cannot be converted to byte
+        if (boxed instanceof byte b) System.out.println("fits a byte: " + b);   // Integer to byte is not allowed
+            ^
+1 error
+Error: Could not find or load main class BoxedToNarrower
+Caused by: java.lang.ClassNotFoundException: BoxedToNarrower
+
+$ javac --enable-preview --release 27 preview/BoxedToNarrower.java && java --enable-preview BoxedToNarrower     (27+35)
+preview/BoxedToNarrower.java:4: error: incompatible types: Integer cannot be converted to byte
+        if (boxed instanceof byte b) System.out.println("fits a byte: " + b);   // Integer to byte is not allowed
+            ^
+1 error
+Error: Could not find or load main class BoxedToNarrower
+Caused by: java.lang.ClassNotFoundException: BoxedToNarrower