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

README.md

@@ -64,6 +64,7 @@ These modules keep only sources, a `run.sh` and their transcripts (`output/`). T
 |---|---|---|
 | [`jep512/`](jep512) | Compact Source Files and Instance Main Methods in Java 25 (JEP 512) | `java Hello.java` on JDK 21 vs 25 vs 27, the class `javac` builds around `void main()`, implicit `java.base` imports, `java.lang.IO`, the measured launch order, a private-constructor difference between 25 and 27 |
 | [`jep513/`](jep513) | Flexible Constructor Bodies in Java 25 (JEP 513): Validate Before super() | statements before `super(...)`/`this(...)`, the parent-calls-child bug and its fix, twelve compile errors that remain with the 25 and 27 wordings side by side, `--release` rejection |
+| [`jep511/`](jep511) | Module Import Declarations in Java 25 (JEP 511) | `import module java.base;` against seven single imports, ambiguity errors and how single-type, on-demand and same-package names beat a module import, what one module import does and does not bring in (`java.sql` does not give `java.base`; `java.se` needs `--add-modules`), named modules, JEP 512 compact files, jshell's default imports, identical bytecode |
 
 ## Captured output (`docs/output/`)
 

jep511/README.md

@@ -0,0 +1,12 @@
+# jep511 — Module Import Declarations (JEP 511, final in Java 25)
+
+Companion code for the ankurm.com article **Module Import Declarations in Java 25 (JEP 511)**. The explanation lives in the article;
+this folder holds the runnable sources and the transcripts they produced.
+
+```bash
+JDK25=/path/to/jdk-25 JDK27=/path/to/jdk-27 [JDK21=/path/to/jdk-21] ./run.sh    # regenerates output/*.txt
+```
+
+`src/` compiles and runs; `broken/` fails to compile on purpose (the diagnostics are captured in `output/`). `multi/` holds three small
+modules (`acme.text` is a library, `demo.app` uses it, `demo.bad` and `demo.noreq` show the two ways to get it wrong). Tested on
+Temurin 25.0.4.1+1 and 27+35; JDK 21 is used only for the "before" error and the jshell import list.

jep511/broken/AmbiguousDate.java

@@ -0,0 +1,9 @@
+import module java.base;
+import module java.sql;
+
+public class AmbiguousDate {
+    public static void main(String[] args) {
+        Date d = new Date(0L);
+        System.out.println(d);
+    }
+}

jep511/broken/AmbiguousList.java

@@ -0,0 +1,10 @@
+import module java.base;
+import module java.desktop;
+
+public class AmbiguousList {
+    public static void main(String[] args) {
+        List<String> names = new ArrayList<>();
+        names.add("x");
+        System.out.println(names);
+    }
+}

jep511/broken/ClassicNoImport.java

@@ -0,0 +1,5 @@
+public class ClassicNoImport {
+    public static void main(String[] args) {
+        System.out.println(List.of("no imports at all"));
+    }
+}

jep511/broken/ModuleInsideClass.java

@@ -0,0 +1,3 @@
+public class ModuleInsideClass {
+    import module java.base;
+}

jep511/broken/NoSuchModule.java

@@ -0,0 +1,5 @@
+import module java.nosuch;
+
+public class NoSuchModule {
+    public static void main(String[] args) { }
+}

jep511/broken/SqlDoesNotGiveBase.java

@@ -0,0 +1,8 @@
+import module java.sql;
+
+public class SqlDoesNotGiveBase {
+    public static void main(String[] args) {
+        List<String> l = List.of("x");     // java.util.List lives in java.base
+        System.out.println(l);
+    }
+}

jep511/multi/acme.text/acme/text/Slug.java

@@ -0,0 +1,6 @@
+package acme.text;
+
+public final class Slug {
+    private Slug() {}
+    public static String of(String s) { return acme.text.internal.Helper.clean(s); }
+}

jep511/multi/acme.text/acme/text/internal/Helper.java

@@ -0,0 +1,5 @@
+package acme.text.internal;
+
+public final class Helper {
+    public static String clean(String s) { return s.toLowerCase().replaceAll("[^a-z0-9]+", "-").replaceAll("^-|-$", ""); }
+}

jep511/multi/acme.text/module-info.java

@@ -0,0 +1,3 @@
+module acme.text {
+    exports acme.text;          // acme.text.internal is NOT exported
+}

jep511/multi/demo.app/demo/App.java

@@ -0,0 +1,9 @@
+package demo;
+
+import module acme.text;     // imports Slug, but not acme.text.internal.Helper
+
+public class App {
+    public static void main(String[] args) {
+        System.out.println(Slug.of("Import Module: Hello, World!"));
+    }
+}

jep511/multi/demo.app/module-info.java

@@ -0,0 +1,3 @@
+module demo.app {
+    requires acme.text;
+}

jep511/multi/demo.bad/demo/Bad.java

@@ -0,0 +1,9 @@
+package demo;
+
+import module acme.text;
+
+public class Bad {
+    public static void main(String[] args) {
+        System.out.println(Helper.clean("x"));      // Helper is in the non-exported acme.text.internal
+    }
+}

jep511/multi/demo.bad/module-info.java

@@ -0,0 +1,3 @@
+module demo.bad {
+    requires acme.text;
+}

jep511/multi/demo.noreq/demo/NoReq.java

@@ -0,0 +1,9 @@
+package demo;
+
+import module java.sql;       // demo.noreq never says "requires java.sql"
+
+public class NoReq {
+    public static void main(String[] args) {
+        System.out.println(Connection.TRANSACTION_NONE);
+    }
+}

jep511/multi/demo.noreq/module-info.java

@@ -0,0 +1 @@
+module demo.noreq { }

jep511/output/01-old-vs-new.txt

@@ -0,0 +1,15 @@
+$ javac src/OldWay.java && java OldWay     (25.0.4.1+1-LTS)
+{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
+a/b/c.txt on 2026-09-15
+
+$ javac src/OldWay.java && java OldWay     (27+35)
+{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
+a/b/c.txt on 2026-09-15
+
+$ javac src/NewWay.java && java NewWay     (25.0.4.1+1-LTS)
+{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
+a/b/c.txt on 2026-09-15
+
+$ javac src/NewWay.java && java NewWay     (27+35)
+{a=[apple, avocado], b=[banana, blueberry], c=[cherry]}
+a/b/c.txt on 2026-09-15

jep511/output/02-ambiguity.txt

@@ -0,0 +1,43 @@
+$ javac broken/AmbiguousDate.java     (25.0.4.1+1-LTS)
+broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
+        Date d = new Date(0L);
+        ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
+        Date d = new Date(0L);
+                     ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+2 errors
+
+$ javac broken/AmbiguousDate.java     (27+35)
+broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
+        Date d = new Date(0L);
+        ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+broken/AmbiguousDate.java:6: error: reference to Date is ambiguous
+        Date d = new Date(0L);
+                     ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+2 errors
+
+$ javac broken/AmbiguousList.java     (25.0.4.1+1-LTS)
+broken/AmbiguousList.java:6: error: reference to List is ambiguous
+        List<String> names = new ArrayList<>();
+        ^
+  both class java.awt.List in java.awt and interface java.util.List in java.util match
+1 error
+
+$ javac broken/AmbiguousList.java     (27+35)
+broken/AmbiguousList.java:6: error: reference to List is ambiguous
+        List<String> names = new ArrayList<>();
+        ^
+  both class java.awt.List in java.awt and interface java.util.List in java.util match
+1 error
+
+$ javac src/FixedDate.java && java FixedDate     (25.0.4.1+1-LTS)
+java.util.Date
+java.sql.Date
+
+$ javac src/FixedDate.java && java FixedDate     (27+35)
+java.util.Date
+java.sql.Date

jep511/output/03-precedence.txt

@@ -0,0 +1,31 @@
+$ javac src/StarImportWins.java && java StarImportWins     (25.0.4.1+1-LTS)
+java.util.Date
+
+$ javac src/StarImportWins.java && java StarImportWins     (27+35)
+java.util.Date
+
+$ javac src/StarImportWinsSql.java && java StarImportWinsSql     (25.0.4.1+1-LTS)
+java.sql.Date
+
+$ javac src/StarImportWinsSql.java && java StarImportWinsSql     (27+35)
+java.sql.Date
+
+$ javac src/SamePackageWins.java && java SamePackageWins     (25.0.4.1+1-LTS)
+my own Date
+java.util.Date
+
+$ javac src/SamePackageWins.java && java SamePackageWins     (27+35)
+my own Date
+java.util.Date
+
+$ javac src/UnusedAmbiguity.java && java UnusedAmbiguity     (25.0.4.1+1-LTS)
+no Date mentioned, no error
+
+$ javac src/UnusedAmbiguity.java && java UnusedAmbiguity     (27+35)
+no Date mentioned, no error
+
+$ javac src/DuplicateImports.java && java DuplicateImports     (25.0.4.1+1-LTS)
+[dups are fine]
+
+$ javac src/DuplicateImports.java && java DuplicateImports     (27+35)
+[dups are fine]

jep511/output/04-what-a-module-import-brings-in.txt

@@ -0,0 +1,71 @@
+$ java --describe-module java.sql     (25.0.4.1+1-LTS)
+[email protected]
+exports java.sql
+exports javax.sql
+requires java.xml transitive
+requires java.logging transitive
+requires java.transaction.xa transitive
+requires java.base mandated
+uses java.sql.Driver
+
+$ java --describe-module java.se | grep -c 'requires'     (25.0.4.1+1-LTS)
+20
+
+$ java --describe-module java.se | grep -c exports     (25.0.4.1+1-LTS)
+0
+
+$ javac src/Transitive.java && java Transitive     (25.0.4.1+1-LTS)
+demo
+0
+java.xml
+[java.base needed its own import]
+
+$ javac src/Transitive.java && java Transitive     (27+35)
+demo
+0
+java.xml
+[java.base needed its own import]
+
+$ javac broken/SqlDoesNotGiveBase.java     (25.0.4.1+1-LTS)
+broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
+        List<String> l = List.of("x");     // java.util.List lives in java.base
+        ^
+  symbol:   class List
+  location: class SqlDoesNotGiveBase
+broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
+        List<String> l = List.of("x");     // java.util.List lives in java.base
+                         ^
+  symbol:   variable List
+  location: class SqlDoesNotGiveBase
+2 errors
+
+$ javac broken/SqlDoesNotGiveBase.java     (27+35)
+broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
+        List<String> l = List.of("x");     // java.util.List lives in java.base
+        ^
+  symbol:   class List
+  location: class SqlDoesNotGiveBase
+broken/SqlDoesNotGiveBase.java:5: error: cannot find symbol
+        List<String> l = List.of("x");     // java.util.List lives in java.base
+                         ^
+  symbol:   variable List
+  location: class SqlDoesNotGiveBase
+2 errors
+
+$ javac src/JavaSe.java     (25.0.4.1+1-LTS)
+src/JavaSe.java:1: error: unnamed module does not read: java.se
+import module java.se;
+^
+1 error
+
+$ javac src/JavaSe.java     (27+35)
+src/JavaSe.java:1: error: unnamed module does not read: java.se
+import module java.se;
+^
+1 error
+
+$ javac --add-modules java.se src/JavaSe.java && java JavaSe     (25.0.4.1+1-LTS)
+[a] x 0
+
+$ javac --add-modules java.se src/JavaSe.java && java JavaSe     (27+35)
+[a] x 0

jep511/output/05-packages-and-modules.txt

@@ -0,0 +1,48 @@
+$ javac src/InPackage.java && java demo.mod.InPackage     (25.0.4.1+1-LTS)
+[1, 2, 3] from package demo.mod
+
+$ javac src/InPackage.java && java demo.mod.InPackage     (27+35)
+[1, 2, 3] from package demo.mod
+
+$ 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)
+import-module-hello-world
+
+$ javac -d out --module-source-path multi --module acme.text,demo.bad     (25.0.4.1+1-LTS)
+multi/demo.bad/demo/Bad.java:7: error: cannot find symbol
+        System.out.println(Helper.clean("x"));      // Helper is in the non-exported acme.text.internal
+                           ^
+  symbol:   variable Helper
+  location: class Bad
+1 error
+
+$ javac -d out --module-source-path multi --module demo.noreq     (25.0.4.1+1-LTS)
+multi/demo.noreq/demo/NoReq.java:3: error: module demo.noreq does not read: java.sql
+import module java.sql;       // demo.noreq never says "requires java.sql"
+^
+1 error
+
+$ javac -d out --module-source-path multi --module acme.text,demo.app && java -p out -m demo.app/demo.App     (27+35)
+import-module-hello-world
+
+$ javac -d out --module-source-path multi --module acme.text,demo.bad     (27+35)
+multi/demo.bad/demo/Bad.java:7: error: cannot find symbol
+        System.out.println(Helper.clean("x"));      // Helper is in the non-exported acme.text.internal
+                           ^
+  symbol:   variable Helper
+  location: class Bad
+1 error
+
+$ javac -d out --module-source-path multi --module demo.noreq     (27+35)
+multi/demo.noreq/demo/NoReq.java:3: error: module demo.noreq does not read: java.sql
+import module java.sql;       // demo.noreq never says "requires java.sql"
+^
+1 error
+
+$ javac -p lib src/ThirdParty.java     (25.0.4.1+1-LTS)
+src/ThirdParty.java:1: error: unnamed module does not read: acme.text
+import module acme.text;
+^
+1 error
+
+$ 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)
+a-script-using-a-library-module

jep511/output/06-compact-files-and-scripts.txt

@@ -0,0 +1,56 @@
+$ javac src/CompactNoImport.java && java CompactNoImport     (25.0.4.1+1-LTS)
+[no imports at all]
+
+$ javac src/CompactNoImport.java && java CompactNoImport     (27+35)
+[no imports at all]
+
+$ javac src/CompactPlusImport.java && java CompactPlusImport     (25.0.4.1+1-LTS)
+[java.base came implicitly] 0
+
+$ javac src/CompactPlusImport.java && java CompactPlusImport     (27+35)
+[java.base came implicitly] 0
+
+$ javac src/CompactAmbiguous.java     (25.0.4.1+1-LTS)
+src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
+    Date d = new Date(0L);      // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
+    ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
+    Date d = new Date(0L);      // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
+                 ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+2 errors
+
+$ javac src/CompactAmbiguous.java     (27+35)
+src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
+    Date d = new Date(0L);      // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
+    ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+src/CompactAmbiguous.java:4: error: reference to Date is ambiguous
+    Date d = new Date(0L);      // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
+                 ^
+  both class java.sql.Date in java.sql and class java.util.Date in java.util match
+2 errors
+
+$ javac broken/ClassicNoImport.java     (25.0.4.1+1-LTS)
+broken/ClassicNoImport.java:3: error: cannot find symbol
+        System.out.println(List.of("no imports at all"));
+                           ^
+  symbol:   variable List
+  location: class ClassicNoImport
+1 error
+
+$ javac broken/ClassicNoImport.java     (27+35)
+broken/ClassicNoImport.java:3: error: cannot find symbol
+        System.out.println(List.of("no imports at all"));
+                           ^
+  symbol:   variable List
+  location: class ClassicNoImport
+1 error
+
+$ java src/Script.java     (25.0.4.1+1-LTS)
+a-b-c 2026-09-15
+
+$ java src/Script.java     (27+35)
+a-b-c 2026-09-15
+

jep511/output/07-bytecode-identical.txt

@@ -0,0 +1,29 @@
+$ diff <(javap -c -p OldWay) <(javap -c -p NewWay)     (25.0.4.1+1-LTS, class name normalised to X)
+no differences (57 lines of javap output each)
+
+$ cmp OldWay.class NewWay.class     (javac -g:none; NewWay renamed to OldWay inside the class file)
+identical, byte for byte (2249 bytes)
+
+$ diff <(javap -c -p -l OldWay) <(javap -c -p -l NewWay)     (default javac -g keeps line numbers)
+8c8
+<         line 9: 0
+---
+>         line 3: 0
+52,57c52,57
+<         line 11: 0
+<         line 12: 14
+<         line 13: 25
+<         line 14: 37
+<         line 15: 44
+<         line 16: 90
+---
+>         line 5: 0
+>         line 6: 14
+>         line 7: 25
+>         line 8: 37
+>         line 9: 44
+>         line 10: 90
+67c67
+<         line 13: 0
+---
+>         line 7: 0

jep511/output/08-errors-and-release-levels.txt

@@ -0,0 +1,60 @@
+$ javac broken/NoSuchModule.java     (25.0.4.1+1-LTS)
+broken/NoSuchModule.java:1: error: imported module not found: java.nosuch
+import module java.nosuch;
+^
+1 error
+
+$ javac broken/NoSuchModule.java     (27+35)
+broken/NoSuchModule.java:1: error: imported module not found: java.nosuch
+import module java.nosuch;
+^
+1 error
+
+$ javac broken/ModuleInsideClass.java     (25.0.4.1+1-LTS)
+broken/ModuleInsideClass.java:2: error: illegal start of type
+    import module java.base;
+    ^
+broken/ModuleInsideClass.java:2: error: ';' expected
+    import module java.base;
+                      ^
+broken/ModuleInsideClass.java:2: error: <identifier> expected
+    import module java.base;
+                           ^
+3 errors
+
+$ javac broken/ModuleInsideClass.java     (27+35)
+broken/ModuleInsideClass.java:2: error: illegal start of type
+    import module java.base;
+    ^
+broken/ModuleInsideClass.java:2: error: ';' expected
+    import module java.base;
+                      ^
+broken/ModuleInsideClass.java:2: error: <identifier> expected
+    import module java.base;
+                           ^
+3 errors
+
+$ javac --release 21 src/NewWay.java     (25.0.4.1+1-LTS)
+src/NewWay.java:1: error: module imports are not supported in -source 21
+import module java.base;
+       ^
+  (use -source 25 or higher to enable module imports)
+1 error
+exit=1
+
+$ javac --release 24 src/NewWay.java     (25.0.4.1+1-LTS)
+src/NewWay.java:1: error: module imports are not supported in -source 24
+import module java.base;
+       ^
+  (use -source 25 or higher to enable module imports)
+1 error
+exit=1
+
+$ javac --release 25 src/NewWay.java     (25.0.4.1+1-LTS)
+exit=0
+
+$ javac src/NewWay.java     (21.0.10+7-Ubuntu-124.04)
+src/NewWay.java:1: error: '.' expected
+import module java.base;
+             ^
+1 error

jep511/output/09-jshell.txt

@@ -0,0 +1,21 @@
+$ jshell --feedback concise src/imports.jsh     (21.0.10+7-Ubuntu-124.04)
+  import java.io.*
+  import java.math.*
+  import java.net.*
+  import java.nio.file.*
+  import java.util.*
+  import java.util.concurrent.*
+  import java.util.function.*
+  import java.util.prefs.*
+  import java.util.regex.*
+  import java.util.stream.*
+[2, 4]
+
+$ jshell --feedback concise src/imports.jsh     (25.0.4.1+1-LTS)
+  import java.base
+[2, 4]
+
+$ jshell --feedback concise src/imports.jsh     (27+35)
+  import java.base
+[2, 4]
+

jep511/run.sh

@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+# JEP 511 (Module Import Declarations): final in JDK 25, no --enable-preview.
+# Regenerates every file in output/.   JDK25=/path JDK27=/path [JDK21=/path] ./run.sh
+set -uo pipefail
+unset JAVA_TOOL_OPTIONS
+HERE="$(cd "$(dirname "$0")" && pwd)"
+JDK25="${JDK25:-/opt/jdks/jdk-25.0.4.1+1}"; JDK27="${JDK27:-/opt/jdks/jdk27}"; JDK21="${JDK21:-}"
+OUT="$HERE/output"; mkdir -p "$OUT"; B="$(mktemp -d)"; trap 'rm -rf "$B"' EXIT
+cd "$HERE"
+# the build string of a JDK, e.g. 25.0.4.1+1-LTS
+t() { "$1/bin/java" -version 2>&1 | sed -n 2p | sed 's/.*(build \(.*\))/\1/'; }
+# compile SRC (extra javac args in $EXTRA) and run CLASS; header names the JDK
+cr() { local jdk="$1" src="$2" cls="$3"; shift 3; local o; o="$(mktemp -d -p "$B")"
+  echo "\$ javac ${*:+$* }$src && java $cls     ($(t "$jdk"))"
+  "$jdk/bin/javac" "$@" -d "$o" "$src" 2>&1 && "$jdk/bin/java" "$@" -cp "$o" "$cls" 2>&1; }
+# compile only: shows the diagnostics
+co() { local jdk="$1" src="$2"; shift 2; local o; o="$(mktemp -d -p "$B")"
+  echo "\$ javac ${*:+$* }$src     ($(t "$jdk"))"
+  "$jdk/bin/javac" "$@" -d "$o" "$src" 2>&1 | grep -v '^Note:'; }
+both() { local fn="$1"; shift; "$fn" "$JDK25" "$@"; echo; "$fn" "$JDK27" "$@"; }
+
+# 01 - the same program with one import line instead of seven
+{ both cr src/OldWay.java OldWay; echo; both cr src/NewWay.java NewWay; } > "$OUT/01-old-vs-new.txt"
+
+# 02 - ambiguity: two modules export a class with the same simple name
+{ both co broken/AmbiguousDate.java; echo; both co broken/AmbiguousList.java; echo; both cr src/FixedDate.java FixedDate; } > "$OUT/02-ambiguity.txt"
+
+# 03 - precedence: who wins when several imports offer the same simple name
+{ both cr src/StarImportWins.java StarImportWins; echo; both cr src/StarImportWinsSql.java StarImportWinsSql; echo
+  both cr src/SamePackageWins.java SamePackageWins; echo; both cr src/UnusedAmbiguity.java UnusedAmbiguity; echo
+  both cr src/DuplicateImports.java DuplicateImports; } > "$OUT/03-precedence.txt"
+
+# 04 - what one module import actually brings in
+{ echo "\$ java --describe-module java.sql     ($(t "$JDK25"))"; "$JDK25/bin/java" --describe-module java.sql; echo
+  echo "\$ java --describe-module java.se | grep -c 'requires'     ($(t "$JDK25"))"; "$JDK25/bin/java" --describe-module java.se | grep -c requires; echo
+  echo "\$ java --describe-module java.se | grep -c exports     ($(t "$JDK25"))"; "$JDK25/bin/java" --describe-module java.se | grep -c exports; echo
+  both cr src/Transitive.java Transitive; echo; both co broken/SqlDoesNotGiveBase.java; echo
+  both co src/JavaSe.java; echo; both cr src/JavaSe.java JavaSe --add-modules java.se; } > "$OUT/04-what-a-module-import-brings-in.txt"
+
+# 05 - packages, named modules and library modules
+{ both cr src/InPackage.java demo.mod.InPackage; echo
+  for j in "$JDK25" "$JDK27"; do o="$(mktemp -d -p "$B")"
+    echo "\$ javac -d out --module-source-path multi --module acme.text,demo.app && java -p out -m demo.app/demo.App     ($(t "$j"))"
+    "$j/bin/javac" -d "$o" --module-source-path multi --module acme.text,demo.app 2>&1 && "$j/bin/java" -p "$o" -m demo.app/demo.App 2>&1; echo
+    echo "\$ javac -d out --module-source-path multi --module acme.text,demo.bad     ($(t "$j"))"
+    "$j/bin/javac" -d "$(mktemp -d -p "$B")" --module-source-path multi --module acme.text,demo.bad 2>&1; echo
+    echo "\$ javac -d out --module-source-path multi --module demo.noreq     ($(t "$j"))"
+    "$j/bin/javac" -d "$(mktemp -d -p "$B")" --module-source-path multi --module demo.noreq 2>&1; echo
+  done
+  lib="$(mktemp -d -p "$B")"; "$JDK25/bin/javac" -d "$lib" --module-source-path multi --module acme.text 2>&1
+  c="$(mktemp -d -p "$B")"
+  echo "\$ javac -p lib src/ThirdParty.java     ($(t "$JDK25"))"; "$JDK25/bin/javac" -p "$lib" -d "$c" src/ThirdParty.java 2>&1; echo
+  echo "\$ javac -p lib --add-modules acme.text src/ThirdParty.java && java -p lib --add-modules acme.text -cp out ThirdParty     ($(t "$JDK25"))"
+  "$JDK25/bin/javac" -p "$lib" --add-modules acme.text -d "$c" src/ThirdParty.java 2>&1 && "$JDK25/bin/java" -p "$lib" --add-modules acme.text -cp "$c" ThirdParty 2>&1
+} > "$OUT/05-packages-and-modules.txt"
+
+# 06 - together with JEP 512 compact source files, and in the source launcher
+{ both cr src/CompactNoImport.java CompactNoImport; echo; both cr src/CompactPlusImport.java CompactPlusImport; echo
+  both co src/CompactAmbiguous.java; echo; both co broken/ClassicNoImport.java; echo
+  for j in "$JDK25" "$JDK27"; do echo "\$ java src/Script.java     ($(t "$j"))"; "$j/bin/java" src/Script.java 2>&1; echo; done
+} > "$OUT/06-compact-files-and-scripts.txt"
+
+# 07 - what the compiler emits: nothing different
+{ o="$(mktemp -d -p "$B")"; "$JDK25/bin/javac" -d "$o" src/OldWay.java src/NewWay.java
+  for c in OldWay NewWay; do "$JDK25/bin/javap" -c -p -cp "$o" "$c" | sed "s/$c/X/g" | grep -v '^Compiled from' > "$o/$c.txt"; done
+  echo "\$ diff <(javap -c -p OldWay) <(javap -c -p NewWay)     ($(t "$JDK25"), class name normalised to X)"
+  diff "$o/OldWay.txt" "$o/NewWay.txt" && echo "no differences ($(wc -l < "$o/OldWay.txt") lines of javap output each)"; echo
+  echo "\$ cmp OldWay.class NewWay.class     (javac -g:none; NewWay renamed to OldWay inside the class file)"
+  "$JDK25/bin/javac" -g:none -d "$o/n" src/OldWay.java src/NewWay.java
+  LC_ALL=C sed 's/NewWay/OldWay/g' "$o/n/NewWay.class" > "$o/NewWay.renamed"
+  cmp "$o/n/OldWay.class" "$o/NewWay.renamed" && echo "identical, byte for byte ($(stat -c %s "$o/n/OldWay.class") bytes)"
+  for c in OldWay NewWay; do "$JDK25/bin/javap" -c -p -l -cp "$o" "$c" | sed "s/$c/X/g" | grep -v '^Compiled from' > "$o/$c.l"; done
+  echo; echo "\$ diff <(javap -c -p -l OldWay) <(javap -c -p -l NewWay)     (default javac -g keeps line numbers)"
+  diff "$o/OldWay.l" "$o/NewWay.l"
+} > "$OUT/07-bytecode-identical.txt"
+
+# 08 - errors that are not about ambiguity, and the language level
+{ both co broken/NoSuchModule.java; echo; both co broken/ModuleInsideClass.java; echo
+  for r in 21 24 25; do echo "\$ javac --release $r src/NewWay.java     ($(t "$JDK25"))"
+    "$JDK25/bin/javac" --release $r -d "$(mktemp -d -p "$B")" src/NewWay.java 2>&1; echo "exit=$?"; echo; done
+  [ -n "$JDK21" ] && co "$JDK21" src/NewWay.java; } > "$OUT/08-errors-and-release-levels.txt"
+
+# 09 - jshell: what it imports for you
+{ for j in ${JDK21:+"$JDK21"} "$JDK25" "$JDK27"; do
+    "$j/bin/jshell" --feedback concise src/imports.jsh >/dev/null 2>&1   # first run creates the prefs dir and logs about it
+    echo "\$ jshell --feedback concise src/imports.jsh     ($(t "$j"))"; "$j/bin/jshell" --feedback concise src/imports.jsh 2>&1; echo; done
+} > "$OUT/09-jshell.txt"
+echo "wrote $OUT"

jep511/src/CompactAmbiguous.java

@@ -0,0 +1,6 @@
+import module java.sql;
+
+void main() {
+    Date d = new Date(0L);      // implicit java.base (java.util.Date) vs explicit java.sql (java.sql.Date)
+    IO.println(d.getClass().getName());
+}

jep511/src/CompactNoImport.java

@@ -0,0 +1,3 @@
+void main() {
+    IO.println(List.of("no imports at all"));
+}

jep511/src/CompactPlusImport.java

@@ -0,0 +1,6 @@
+import module java.sql;
+
+void main() {
+    var l = List.of("java.base came implicitly");      // no import module java.base written
+    IO.println(l + " " + Connection.TRANSACTION_NONE);  // java.sql from the explicit import
+}

jep511/src/DuplicateImports.java

@@ -0,0 +1,10 @@
+import module java.base;
+import module java.base;
+import java.util.List;
+import java.util.List;
+
+public class DuplicateImports {
+    public static void main(String[] args) {
+        System.out.println(List.of("dups are fine"));
+    }
+}

jep511/src/FixedDate.java

@@ -0,0 +1,12 @@
+import module java.base;
+import module java.sql;
+import java.util.Date;          // a single-type import wins over both module imports
+
+public class FixedDate {
+    public static void main(String[] args) {
+        Date d = new Date(0L);
+        System.out.println(d.getClass().getName());
+        java.sql.Date s = new java.sql.Date(0L);   // the other one is still reachable by its full name
+        System.out.println(s.getClass().getName());
+    }
+}

jep511/src/InPackage.java

@@ -0,0 +1,9 @@
+package demo.mod;
+
+import module java.base;
+
+public class InPackage {
+    public static void main(String[] args) {
+        System.out.println(List.of(1, 2, 3) + " from package " + InPackage.class.getPackageName());
+    }
+}

jep511/src/JavaSe.java

@@ -0,0 +1,10 @@
+import module java.se;
+import java.util.List;                  // java.se brings in java.desktop, whose java.awt.List clashes with java.util.List
+
+public class JavaSe {
+    public static void main(String[] args) {
+        List<String> l = List.of("a");                    // java.base
+        Logger lg = Logger.getLogger("x");                // java.logging
+        System.out.println(l + " " + lg.getName() + " " + Connection.TRANSACTION_NONE);  // java.sql
+    }
+}

jep511/src/NewWay.java

@@ -0,0 +1,11 @@
+import module java.base;
+
+public class NewWay {
+    public static void main(String[] args) {
+        List<String> words = List.of("apple", "avocado", "banana", "blueberry", "cherry");
+        Map<Character, List<String>> byInitial = words.stream()
+                .collect(Collectors.groupingBy(w -> w.charAt(0)));
+        System.out.println(byInitial);
+        System.out.println(Path.of("a", "b", "c.txt") + " on " + LocalDate.of(2026, 9, 15));
+    }
+}

jep511/src/OldWay.java

@@ -0,0 +1,17 @@
+import java.nio.file.Path;
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class OldWay {
+    public static void main(String[] args) {
+        List<String> words = List.of("apple", "avocado", "banana", "blueberry", "cherry");
+        Map<Character, List<String>> byInitial = words.stream()
+                .collect(Collectors.groupingBy(w -> w.charAt(0)));
+        System.out.println(byInitial);
+        System.out.println(Path.of("a", "b", "c.txt") + " on " + LocalDate.of(2026, 9, 15));
+    }
+}

jep511/src/SamePackageWins.java

@@ -0,0 +1,12 @@
+import module java.base;
+
+class Date {                       // a class in this file's own package
+    public String toString() { return "my own Date"; }
+}
+
+public class SamePackageWins {
+    public static void main(String[] args) {
+        System.out.println(new Date());                 // which Date?
+        System.out.println(new java.util.Date(0L).getClass().getName());
+    }
+}

jep511/src/Script.java

@@ -0,0 +1,6 @@
+import module java.base;
+
+void main() {
+    var now = LocalDate.of(2026, 9, 15);
+    IO.println(Stream.of("a", "b", "c").collect(Collectors.joining("-")) + " " + now);
+}

jep511/src/StarImportWins.java

@@ -0,0 +1,9 @@
+import java.util.*;
+import module java.sql;
+
+public class StarImportWins {
+    public static void main(String[] args) {
+        Date d = new Date(0L);
+        System.out.println(d.getClass().getName());
+    }
+}

jep511/src/StarImportWinsSql.java

@@ -0,0 +1,9 @@
+import java.sql.*;
+import module java.base;
+
+public class StarImportWinsSql {
+    public static void main(String[] args) {
+        Date d = new Date(0L);
+        System.out.println(d.getClass().getName());
+    }
+}

jep511/src/ThirdParty.java

@@ -0,0 +1,5 @@
+import module acme.text;
+
+void main() {
+    IO.println(Slug.of("A script using a library module"));
+}

jep511/src/Transitive.java

@@ -0,0 +1,15 @@
+import module java.base;
+import module java.sql;
+
+public class Transitive {
+    public static void main(String[] args) {
+        // java.sql declares "requires transitive" java.logging, java.xml and java.transaction.xa,
+        // so importing java.sql also imports their exported packages.
+        Logger log = Logger.getLogger("demo");                     // java.util.logging   (java.logging)
+        System.out.println(log.getName());
+        System.out.println(XAResource.TMNOFLAGS);                  // javax.transaction.xa (java.transaction.xa)
+        System.out.println(DocumentBuilderFactory.class.getModule().getName());  // javax.xml.parsers (java.xml)
+        List<String> l = List.of("java.base needed its own import");
+        System.out.println(l);
+    }
+}

jep511/src/UnusedAmbiguity.java

@@ -0,0 +1,9 @@
+import module java.base;
+import module java.sql;
+
+public class UnusedAmbiguity {
+    public static void main(String[] args) {
+        // Date is ambiguous between the two modules, but it is never used here, so this compiles.
+        System.out.println("no Date mentioned, no error");
+    }
+}

jep511/src/imports.jsh

@@ -0,0 +1,3 @@
+/imports
+System.out.println(List.of(1, 2).stream().map(x -> x * 2).collect(Collectors.toList()))
+/exit