Add jep511 module: module import declarations on JDK 25 and 27
Runnable sources, deliberate compile failures, three small modules and nine captured transcripts for import module (JEP 511). Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a
This commit is contained in:
Claude
@@ -0,0 +1,15 @@
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$ javac src/OldWay.java && java OldWay (25.0.4.1+1-LTS)
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{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
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a/b/c.txt on 2026-09-15
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$ javac src/OldWay.java && java OldWay (27+35)
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{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
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a/b/c.txt on 2026-09-15
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$ javac src/NewWay.java && java NewWay (25.0.4.1+1-LTS)
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{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
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a/b/c.txt on 2026-09-15
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$ javac src/NewWay.java && java NewWay (27+35)
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{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
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a/b/c.txt on 2026-09-15
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@@ -0,0 +1,43 @@
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$ javac broken/AmbiguousDate.java (25.0.4.1+1-LTS)
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broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
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Date d = new Date(0L);
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
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Date d = new Date(0L);
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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2 errors
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$ javac broken/AmbiguousDate.java (27+35)
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broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
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Date d = new Date(0L);
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
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Date d = new Date(0L);
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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2 errors
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$ javac broken/AmbiguousList.java (25.0.4.1+1-LTS)
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broken/AmbiguousList.java:6: error: reference to List is ambiguous
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List<String> names = new ArrayList<>();
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^
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both class java.awt.List in java.awt and interface java.util.List in java.util match
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1 error
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$ javac broken/AmbiguousList.java (27+35)
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broken/AmbiguousList.java:6: error: reference to List is ambiguous
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List<String> names = new ArrayList<>();
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^
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both class java.awt.List in java.awt and interface java.util.List in java.util match
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1 error
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$ javac src/FixedDate.java && java FixedDate (25.0.4.1+1-LTS)
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java.util.Date
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java.sql.Date
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$ javac src/FixedDate.java && java FixedDate (27+35)
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java.util.Date
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java.sql.Date
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@@ -0,0 +1,31 @@
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$ javac src/StarImportWins.java && java StarImportWins (25.0.4.1+1-LTS)
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java.util.Date
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$ javac src/StarImportWins.java && java StarImportWins (27+35)
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java.util.Date
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$ javac src/StarImportWinsSql.java && java StarImportWinsSql (25.0.4.1+1-LTS)
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java.sql.Date
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$ javac src/StarImportWinsSql.java && java StarImportWinsSql (27+35)
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java.sql.Date
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$ javac src/SamePackageWins.java && java SamePackageWins (25.0.4.1+1-LTS)
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my own Date
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java.util.Date
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$ javac src/SamePackageWins.java && java SamePackageWins (27+35)
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my own Date
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java.util.Date
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$ javac src/UnusedAmbiguity.java && java UnusedAmbiguity (25.0.4.1+1-LTS)
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no Date mentioned, no error
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$ javac src/UnusedAmbiguity.java && java UnusedAmbiguity (27+35)
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no Date mentioned, no error
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$ javac src/DuplicateImports.java && java DuplicateImports (25.0.4.1+1-LTS)
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[dups are fine]
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$ javac src/DuplicateImports.java && java DuplicateImports (27+35)
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[dups are fine]
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@@ -0,0 +1,71 @@
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$ java --describe-module java.sql (25.0.4.1+1-LTS)
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[email protected]
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exports java.sql
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exports javax.sql
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requires java.xml transitive
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requires java.logging transitive
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requires java.transaction.xa transitive
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requires java.base mandated
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uses java.sql.Driver
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$ java --describe-module java.se | grep -c 'requires' (25.0.4.1+1-LTS)
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20
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$ java --describe-module java.se | grep -c exports (25.0.4.1+1-LTS)
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0
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$ javac src/Transitive.java && java Transitive (25.0.4.1+1-LTS)
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demo
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0
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java.xml
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[java.base needed its own import]
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$ javac src/Transitive.java && java Transitive (27+35)
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demo
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0
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java.xml
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[java.base needed its own import]
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$ javac broken/SqlDoesNotGiveBase.java (25.0.4.1+1-LTS)
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broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
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List<String> l = List.of("x"); // java.util.List lives in java.base
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^
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symbol: class List
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location: class SqlDoesNotGiveBase
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broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
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List<String> l = List.of("x"); // java.util.List lives in java.base
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^
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symbol: variable List
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location: class SqlDoesNotGiveBase
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2 errors
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$ javac broken/SqlDoesNotGiveBase.java (27+35)
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broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
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List<String> l = List.of("x"); // java.util.List lives in java.base
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^
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symbol: class List
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location: class SqlDoesNotGiveBase
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broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
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List<String> l = List.of("x"); // java.util.List lives in java.base
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^
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symbol: variable List
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location: class SqlDoesNotGiveBase
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2 errors
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$ javac src/JavaSe.java (25.0.4.1+1-LTS)
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src/JavaSe.java:1: error: unnamed module does not read: java.se
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import module java.se;
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^
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1 error
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$ javac src/JavaSe.java (27+35)
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src/JavaSe.java:1: error: unnamed module does not read: java.se
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import module java.se;
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^
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1 error
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$ javac --add-modules java.se src/JavaSe.java && java JavaSe (25.0.4.1+1-LTS)
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[a] x 0
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$ javac --add-modules java.se src/JavaSe.java && java JavaSe (27+35)
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[a] x 0
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@@ -0,0 +1,48 @@
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$ javac src/InPackage.java && java demo.mod.InPackage (25.0.4.1+1-LTS)
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[1, 2, 3] from package demo.mod
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$ javac src/InPackage.java && java demo.mod.InPackage (27+35)
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[1, 2, 3] from package demo.mod
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$ javac -d out --module-source-path multi --module acme.text,demo.app && java -p out -m demo.app/demo.App (25.0.4.1+1-LTS)
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import-module-hello-world
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$ javac -d out --module-source-path multi --module acme.text,demo.bad (25.0.4.1+1-LTS)
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multi/demo.bad/demo/Bad.java:7: error: cannot find symbol
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System.out.println(Helper.clean("x")); // Helper is in the non-exported acme.text.internal
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^
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symbol: variable Helper
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location: class Bad
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1 error
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$ javac -d out --module-source-path multi --module demo.noreq (25.0.4.1+1-LTS)
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multi/demo.noreq/demo/NoReq.java:3: error: module demo.noreq does not read: java.sql
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import module java.sql; // demo.noreq never says "requires java.sql"
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^
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1 error
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$ javac -d out --module-source-path multi --module acme.text,demo.app && java -p out -m demo.app/demo.App (27+35)
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import-module-hello-world
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$ javac -d out --module-source-path multi --module acme.text,demo.bad (27+35)
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multi/demo.bad/demo/Bad.java:7: error: cannot find symbol
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System.out.println(Helper.clean("x")); // Helper is in the non-exported acme.text.internal
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^
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symbol: variable Helper
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location: class Bad
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1 error
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$ javac -d out --module-source-path multi --module demo.noreq (27+35)
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multi/demo.noreq/demo/NoReq.java:3: error: module demo.noreq does not read: java.sql
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import module java.sql; // demo.noreq never says "requires java.sql"
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^
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1 error
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$ javac -p lib src/ThirdParty.java (25.0.4.1+1-LTS)
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src/ThirdParty.java:1: error: unnamed module does not read: acme.text
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import module acme.text;
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^
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1 error
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$ javac -p lib --add-modules acme.text src/ThirdParty.java && java -p lib --add-modules acme.text -cp out ThirdParty (25.0.4.1+1-LTS)
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a-script-using-a-library-module
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@@ -0,0 +1,56 @@
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$ javac src/CompactNoImport.java && java CompactNoImport (25.0.4.1+1-LTS)
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[no imports at all]
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$ javac src/CompactNoImport.java && java CompactNoImport (27+35)
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[no imports at all]
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$ javac src/CompactPlusImport.java && java CompactPlusImport (25.0.4.1+1-LTS)
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[java.base came implicitly] 0
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$ javac src/CompactPlusImport.java && java CompactPlusImport (27+35)
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[java.base came implicitly] 0
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$ javac src/CompactAmbiguous.java (25.0.4.1+1-LTS)
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src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
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Date d = new Date(0L); // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
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Date d = new Date(0L); // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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2 errors
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$ javac src/CompactAmbiguous.java (27+35)
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src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
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Date d = new Date(0L); // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
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Date d = new Date(0L); // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
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^
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both class java.sql.Date in java.sql and class java.util.Date in java.util match
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2 errors
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$ javac broken/ClassicNoImport.java (25.0.4.1+1-LTS)
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broken/ClassicNoImport.java:3: error: cannot find symbol
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System.out.println(List.of("no imports at all"));
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^
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symbol: variable List
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location: class ClassicNoImport
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1 error
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$ javac broken/ClassicNoImport.java (27+35)
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broken/ClassicNoImport.java:3: error: cannot find symbol
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System.out.println(List.of("no imports at all"));
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^
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symbol: variable List
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location: class ClassicNoImport
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1 error
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$ java src/Script.java (25.0.4.1+1-LTS)
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a-b-c 2026-09-15
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$ java src/Script.java (27+35)
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a-b-c 2026-09-15
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@@ -0,0 +1,29 @@
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$ diff <(javap -c -p OldWay) <(javap -c -p NewWay) (25.0.4.1+1-LTS, class name normalised to X)
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no differences (57 lines of javap output each)
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$ cmp OldWay.class NewWay.class (javac -g:none; NewWay renamed to OldWay inside the class file)
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identical, byte for byte (2249 bytes)
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$ diff <(javap -c -p -l OldWay) <(javap -c -p -l NewWay) (default javac -g keeps line numbers)
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8c8
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< line 9: 0
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---
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> line 3: 0
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52,57c52,57
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< line 11: 0
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< line 12: 14
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< line 13: 25
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< line 14: 37
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< line 15: 44
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< line 16: 90
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---
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> line 5: 0
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> line 6: 14
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> line 7: 25
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> line 8: 37
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> line 9: 44
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> line 10: 90
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67c67
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< line 13: 0
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---
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> line 7: 0
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@@ -0,0 +1,60 @@
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$ javac broken/NoSuchModule.java (25.0.4.1+1-LTS)
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broken/NoSuchModule.java:1: error: imported module not found: java.nosuch
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import module java.nosuch;
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^
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1 error
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$ javac broken/NoSuchModule.java (27+35)
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broken/NoSuchModule.java:1: error: imported module not found: java.nosuch
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import module java.nosuch;
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^
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1 error
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$ javac broken/ModuleInsideClass.java (25.0.4.1+1-LTS)
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broken/ModuleInsideClass.java:2: error: illegal start of type
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import module java.base;
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^
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broken/ModuleInsideClass.java:2: error: ';' expected
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import module java.base;
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^
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broken/ModuleInsideClass.java:2: error: <identifier> expected
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import module java.base;
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^
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3 errors
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$ javac broken/ModuleInsideClass.java (27+35)
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broken/ModuleInsideClass.java:2: error: illegal start of type
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import module java.base;
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^
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broken/ModuleInsideClass.java:2: error: ';' expected
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import module java.base;
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^
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broken/ModuleInsideClass.java:2: error: <identifier> expected
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import module java.base;
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^
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3 errors
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$ javac --release 21 src/NewWay.java (25.0.4.1+1-LTS)
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src/NewWay.java:1: error: module imports are not supported in -source 21
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import module java.base;
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^
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(use -source 25 or higher to enable module imports)
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1 error
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exit=1
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$ javac --release 24 src/NewWay.java (25.0.4.1+1-LTS)
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src/NewWay.java:1: error: module imports are not supported in -source 24
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import module java.base;
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^
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(use -source 25 or higher to enable module imports)
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1 error
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exit=1
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$ javac --release 25 src/NewWay.java (25.0.4.1+1-LTS)
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exit=0
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$ javac src/NewWay.java (21.0.10+7-Ubuntu-124.04)
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src/NewWay.java:1: error: '.' expected
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import module java.base;
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^
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1 error
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@@ -0,0 +1,21 @@
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$ jshell --feedback concise src/imports.jsh (21.0.10+7-Ubuntu-124.04)
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import java.io.*
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import java.math.*
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import java.net.*
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import java.nio.file.*
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import java.util.*
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import java.util.concurrent.*
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import java.util.function.*
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import java.util.prefs.*
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import java.util.regex.*
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import java.util.stream.*
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[2, 4]
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$ jshell --feedback concise src/imports.jsh (25.0.4.1+1-LTS)
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import java.base
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[2, 4]
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$ jshell --feedback concise src/imports.jsh (27+35)
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import java.base
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[2, 4]
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Block a user