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
This commit is contained in:
Claude
@@ -0,0 +1,23 @@
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$ javac src/TypePatterns.java && java TypePatterns (21.0.10+7-Ubuntu-124.04)
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string of length 5 / string of length 5
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3 -1
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int 42
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string JAVA
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int array of 3
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other Double
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$ javac src/TypePatterns.java && java TypePatterns (25.0.4.1+1-LTS)
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string of length 5 / string of length 5
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3 -1
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int 42
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string JAVA
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int array of 3
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other Double
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$ javac src/TypePatterns.java && java TypePatterns (27+35)
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string of length 5 / string of length 5
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3 -1
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int 42
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string JAVA
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int array of 3
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other Double
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@@ -0,0 +1,39 @@
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$ javac src/Guards.java && java Guards (25.0.4.1+1-LTS)
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empty string
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short string: abc
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long string: abcdefgh
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negative -4
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int 12
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other
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$ javac src/Guards.java && java Guards (27+35)
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empty string
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short string: abc
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long string: abcdefgh
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negative -4
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int 12
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other
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$ javac broken/Dominated.java (25.0.4.1+1-LTS)
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broken/Dominated.java:5: error: this case label is dominated by a preceding case label
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case String s -> "string"; // String is a CharSequence, so this can never be reached
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^
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1 error
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$ javac broken/Dominated.java (27+35)
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broken/Dominated.java:5: error: this case label is dominated by a preceding case label
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case String s -> "string"; // String is a CharSequence, so this can never be reached
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^
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1 error
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$ javac broken/GuardBeforeGeneral.java (25.0.4.1+1-LTS)
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broken/GuardBeforeGeneral.java:5: error: this case label is dominated by a preceding case label
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case String s when s.isEmpty() -> "empty string"; // guarded case after the unguarded one
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^
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1 error
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$ javac broken/GuardBeforeGeneral.java (27+35)
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broken/GuardBeforeGeneral.java:5: error: this case label is dominated by a preceding case label
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case String s when s.isEmpty() -> "empty string"; // guarded case after the unguarded one
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^
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1 error
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@@ -0,0 +1,31 @@
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$ javac src/RecordPatterns.java && java RecordPatterns (21.0.10+7-Ubuntu-124.04)
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point at 3,4
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not a point
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7
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box of string hi
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box of int 7
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box of 2.5
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$ javac src/RecordPatterns.java && java RecordPatterns (25.0.4.1+1-LTS)
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point at 3,4
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not a point
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7
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box of string hi
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box of int 7
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box of 2.5
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$ javac src/RecordPatterns.java && java RecordPatterns (27+35)
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point at 3,4
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not a point
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7
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box of string hi
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box of int 7
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box of 2.5
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$ javac src/MatchExceptionDemo.java && java MatchExceptionDemo (25.0.4.1+1-LTS)
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MatchException: java.lang.IllegalStateException: accessor blew up
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cause: java.lang.IllegalStateException: accessor blew up
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$ javac src/MatchExceptionDemo.java && java MatchExceptionDemo (27+35)
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MatchException: java.lang.IllegalStateException: accessor blew up
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cause: java.lang.IllegalStateException: accessor blew up
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@@ -0,0 +1,54 @@
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$ javac src/SealedExhaustive.java && java SealedExhaustive (21.0.10+7-Ubuntu-124.04)
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Circle[r=1.0] -> 3.14
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Square[side=2.0] -> 4.00
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Rect[w=2.0, h=3.0] -> 6.00
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$ javac src/SealedExhaustive.java && java SealedExhaustive (25.0.4.1+1-LTS)
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Circle[r=1.0] -> 3.14
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Square[side=2.0] -> 4.00
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Rect[w=2.0, h=3.0] -> 6.00
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$ javac src/SealedExhaustive.java && java SealedExhaustive (27+35)
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Circle[r=1.0] -> 3.14
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Square[side=2.0] -> 4.00
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Rect[w=2.0, h=3.0] -> 6.00
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$ javac broken/NotExhaustive.java (21.0.10+7-Ubuntu-124.04)
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broken/NotExhaustive.java:8: error: the switch expression does not cover all possible input values
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return switch (s) {
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^
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1 error
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$ javac broken/NotExhaustive.java (25.0.4.1+1-LTS)
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broken/NotExhaustive.java:8: error: the switch expression does not cover all possible input values
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return switch (s) {
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^
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1 error
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$ javac broken/NotExhaustive.java (27+35)
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broken/NotExhaustive.java:8: error: the switch expression does not cover all possible input values
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return switch (s) {
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^
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missing patterns:
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Rect _
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1 error
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$ javac broken/NotExhaustiveObject.java (21.0.10+7-Ubuntu-124.04)
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broken/NotExhaustiveObject.java:3: error: the switch expression does not cover all possible input values
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return switch (o) {
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^
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1 error
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$ javac broken/NotExhaustiveObject.java (25.0.4.1+1-LTS)
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broken/NotExhaustiveObject.java:3: error: the switch expression does not cover all possible input values
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return switch (o) {
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^
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1 error
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$ javac broken/NotExhaustiveObject.java (27+35)
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broken/NotExhaustiveObject.java:3: error: the switch expression does not cover all possible input values
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return switch (o) {
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^
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missing patterns:
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Object _
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1 error
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@@ -0,0 +1,32 @@
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$ java -cp old Client (Client and Shape compiled together, v1) (25.0.4.1+1-LTS)
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circle: 3.141592653589793
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square: 4.0
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$ java -cp new:old Main (Shape gained Triangle; Client.class NOT recompiled) (25.0.4.1+1-LTS)
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Exception in thread "main" java.lang.MatchException
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at Client.area(Client.java:4)
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at Main.main(Main.java:4)
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$ javac -cp new sep/client/Client.java (now recompile Client against v2) (25.0.4.1+1-LTS)
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sep/client/Client.java:4: error: the switch expression does not cover all possible input values
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return switch (s) {
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^
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1 error
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$ java -cp old Client (Client and Shape compiled together, v1) (27+35)
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circle: 3.141592653589793
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square: 4.0
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$ java -cp new:old Main (Shape gained Triangle; Client.class NOT recompiled) (27+35)
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Exception in thread "main" java.lang.MatchException
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at Client.area(Client.java:4)
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at Main.main(Main.java:4)
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$ javac -cp new sep/client/Client.java (now recompile Client against v2) (27+35)
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sep/client/Client.java:4: error: the switch expression does not cover all possible input values
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return switch (s) {
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^
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missing patterns:
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Triangle _
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1 error
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@@ -0,0 +1,26 @@
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$ javac src/NullCase.java && java NullCase (25.0.4.1+1-LTS)
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without case null: NullPointerException
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with case null: null!
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case null, default: null or something else
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instanceof with null: false
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$ javac src/NullCase.java && java NullCase (27+35)
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without case null: NullPointerException
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with case null: null!
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case null, default: null or something else
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instanceof with null: false
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$ javac src/Unnamed.java && java Unnamed (21.0.10+7-Ubuntu-124.04)
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src/Unnamed.java:9: error: unnamed variables are a preview feature and are disabled by default.
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case Circle _ -> "round"; // the type matters, the value does not
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^
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(use --enable-preview to enable unnamed variables)
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1 error
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$ javac src/Unnamed.java && java Unnamed (25.0.4.1+1-LTS)
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round angular
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5
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$ javac src/Unnamed.java && java Unnamed (27+35)
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round angular
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5
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@@ -0,0 +1,87 @@
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$ javac preview/PrimitiveInstanceof.java (25.0.4.1+1-LTS)
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preview/PrimitiveInstanceof.java:3: error: primitive patterns are a preview feature and are disabled by default.
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if (i instanceof byte b) return i + " fits in a byte: " + b;
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^
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(use --enable-preview to enable primitive patterns)
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1 error
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$ javac preview/PrimitiveInstanceof.java (27+35)
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preview/PrimitiveInstanceof.java:3: error: primitive patterns are a preview feature and are disabled by default.
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if (i instanceof byte b) return i + " fits in a byte: " + b;
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^
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(use --enable-preview to enable primitive patterns)
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1 error
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$ javac --enable-preview --release 25 preview/PrimitiveInstanceof.java && java --enable-preview PrimitiveInstanceof (25.0.4.1+1-LTS)
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100 fits in a byte: 100
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1000 fits in a short: 1000
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100000 needs an int
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0.5 converts to float 0.5 without loss
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0.1 does NOT convert to float without loss
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$ javac --enable-preview --release 27 preview/PrimitiveInstanceof.java && java --enable-preview PrimitiveInstanceof (27+35)
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100 fits in a byte: 100
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1000 fits in a short: 1000
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100000 needs an int
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0.5 converts to float 0.5 without loss
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0.1 does NOT convert to float without loss
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$ javac --enable-preview --release 25 preview/PrimitiveSwitch.java && java --enable-preview PrimitiveSwitch (25.0.4.1+1-LTS)
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OK | other success 204 | client error 404 | something else 500
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yes no
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zero one many (9223372036854775807)
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$ javac --enable-preview --release 27 preview/PrimitiveSwitch.java && java --enable-preview PrimitiveSwitch (27+35)
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OK | other success 204 | client error 404 | something else 500
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yes no
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zero one many (9223372036854775807)
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$ javac --enable-preview --release 25 preview/PrimitiveInRecord.java && java --enable-preview PrimitiveInRecord (25.0.4.1+1-LTS)
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whole degrees: 21
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fractional: 21.5
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not a reading
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$ javac --enable-preview --release 27 preview/PrimitiveInRecord.java && java --enable-preview PrimitiveInRecord (27+35)
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whole degrees: 21
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fractional: 21.5
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not a reading
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$ javac --enable-preview --release 25 preview/PrimitiveEdges.java && java --enable-preview PrimitiveEdges (25.0.4.1+1-LTS)
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0.0 int? true float? true
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-0.0 int? false float? true
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NaN int? false float? true
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1.6777217E7 int? true float? false
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1.0E10 int? false float? true
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3.0 int? true float? true
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1099511627776 instanceof int? false
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Object holding Integer matches int pattern: 42
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Short in Object does not match int
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65 as char: A
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$ javac --enable-preview --release 27 preview/PrimitiveEdges.java && java --enable-preview PrimitiveEdges (27+35)
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0.0 int? true float? true
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-0.0 int? false float? true
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NaN int? false float? true
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1.6777217E7 int? true float? false
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1.0E10 int? false float? true
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3.0 int? true float? true
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1099511627776 instanceof int? false
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Object holding Integer matches int pattern: 42
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Short in Object does not match int
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65 as char: A
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$ javac --enable-preview --release 25 preview/BoxedToNarrower.java && java --enable-preview BoxedToNarrower (25.0.4.1+1-LTS)
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preview/BoxedToNarrower.java:4: error: incompatible types: Integer cannot be converted to byte
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if (boxed instanceof byte b) System.out.println("fits a byte: " + b); // Integer to byte is not allowed
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^
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1 error
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Error: Could not find or load main class BoxedToNarrower
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Caused by: java.lang.ClassNotFoundException: BoxedToNarrower
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$ javac --enable-preview --release 27 preview/BoxedToNarrower.java && java --enable-preview BoxedToNarrower (27+35)
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preview/BoxedToNarrower.java:4: error: incompatible types: Integer cannot be converted to byte
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if (boxed instanceof byte b) System.out.println("fits a byte: " + b); // Integer to byte is not allowed
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^
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1 error
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Error: Could not find or load main class BoxedToNarrower
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Caused by: java.lang.ClassNotFoundException: BoxedToNarrower
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@@ -0,0 +1,11 @@
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$ javap -v PrimitiveSwitch | grep -E 'minor|major' (compiled by 25.0.4.1+1-LTS with --enable-preview)
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minor version: 65535
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major version: 69
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$ java --enable-preview PrimitiveSwitch (class compiled on 25, run on 27+35)
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Error: LinkageError occurred while loading main class PrimitiveSwitch
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java.lang.UnsupportedClassVersionError: PrimitiveSwitch (class file version 69.65535) was compiled with preview features that are unsupported. This version of the Java Runtime only recognizes preview features for class file version 71.65535
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$ java PrimitiveSwitch (same class, no flag, run on 25.0.4.1+1-LTS)
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Error: LinkageError occurred while loading main class PrimitiveSwitch
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java.lang.UnsupportedClassVersionError: Preview features are not enabled for PrimitiveSwitch (class file version 69.65535). Try running with '--enable-preview'
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