Add java21-features module: runnable demos and captured output for the ankurm.com java21-features article

2026-10-20 17:13:59 +00:00
parent 5a076c826f
commit c3cc57f482
33 changed files with 354 additions and 0 deletions
@@ -0,0 +1,5 @@
+$ javac  src/VirtualThreadsDemo.java && java  VirtualThreadsDemo     (21.0.12.1)
+tasks completed : 10000
+finished in < 5s: true   (10,000 x 1s sleeps)
+isVirtual       : true, daemon=true
+platform isVirtual: false
@@ -0,0 +1,5 @@
+$ javac  src/RecordPatternsDemo.java && java  RecordPatternsDemo     (21.0.12.1)
+line from (0,0) to (3,4) length^2=25
+box of String hi
+box of Integer 7
+no match
@@ -0,0 +1,3 @@
+$ javac  src/PatternSwitchDemo.java && java  PatternSwitchDemo     (21.0.12.1)
+big circle | circle | square 2.0 | rect 2.0x3.0
+null handled in the switch | large int | int | string of 4 | other
@@ -0,0 +1,11 @@
+$ javac  src/SequencedCollectionsDemo.java && java  SequencedCollectionsDemo     (21.0.12.1)
+getFirst/getLast: a c
+reversed view   : [c, b, a]
+addFirst+removeLast: [z, a, b]
+LinkedHashSet reversed: [3, 2, 1]
+firstEntry/lastEntry : x=1 z=3
+putFirst        : {w=0, x=1, y=2, z=3}
+reversed map    : {z=3, y=2, x=1, w=0}
+view sees add   : [3, 2, 1]
+immutable list : UnsupportedOperationException
+HashSet         : no getFirst (unordered)
@@ -0,0 +1,5 @@
+$ javac  src/KemDemo.java && java  KemDemo     (21.0.12.1)
+algorithm       : DHKEM
+secrets equal   : true
+secret length   : 32 bytes
+ciphertext length: 32 bytes
@@ -0,0 +1,9 @@
+$ javac  src/GcNamesDemo.java && java -XX:+UseZGC GcNamesDemo     (21.0.12.1)
+gc bean         : ZGC Cycles
+gc bean         : ZGC Pauses
+
+$ javac  src/GcNamesDemo.java && java -XX:+UseZGC -XX:+ZGenerational GcNamesDemo     (21.0.12.1)
+gc bean         : ZGC Minor Cycles
+gc bean         : ZGC Minor Pauses
+gc bean         : ZGC Major Cycles
+gc bean         : ZGC Major Pauses
@@ -0,0 +1,6 @@
+$ javac --add-modules jdk.incubator.vector src/VectorDemo.java && java --add-modules jdk.incubator.vector VectorDemo     (21.0.12.1)
+warning: using incubating module(s): jdk.incubator.vector
+1 warning
+WARNING: Using incubator modules: jdk.incubator.vector
+vector == scalar: true
+lanes >= 2      : true
@@ -0,0 +1,2 @@
+$ javac --release 21 --enable-preview src/StringTemplatesPreview.java && java --enable-preview StringTemplatesPreview     (21.0.12.1)
+Hello Ankur, 3 + 4 = 7
@@ -0,0 +1,4 @@
+$ javac --release 21 --enable-preview src/UnnamedPreview.java && java --enable-preview UnnamedPreview     (21.0.12.1)
+x only         : 5
+loop count      : 3
+caught, name not needed
@@ -0,0 +1,2 @@
+$ java --enable-preview --source 21 src/UnnamedMainPreview.java     (21.0.12.1)
+no class, no static, no String[] args
@@ -0,0 +1,3 @@
+$ javac --release 21 --enable-preview src/ScopedValuesPreview.java && java --enable-preview ScopedValuesPreview     (21.0.12.1)
+inside handler  : user=ankur
+outside         : bound=false
@@ -0,0 +1,3 @@
+$ javac --release 21 --enable-preview src/StructuredConcurrencyPreview.java && java --enable-preview StructuredConcurrencyPreview     (21.0.12.1)
+both subtasks   : ankur / 42
+failure shuts down siblings: java.lang.IllegalStateException: boom
@@ -0,0 +1,2 @@
+$ javac --release 21 --enable-preview src/FfmPreview.java && java --enable-preview --enable-native-access=ALL-UNNAMED FfmPreview     (21.0.12.1)
+strlen("Hello Ankur") = 11
@@ -0,0 +1,18 @@
+$ javac  broken/PreviewWithoutFlag.java     (21.0.12.1)
+broken/PreviewWithoutFlag.java:3: error: string templates are a preview feature and are disabled by default.
+    public static void main(String[] args) { String n = "x"; System.out.println(STR."hi \{n}"); }
+                                                                                    ^
+  (use --enable-preview to enable string templates)
+1 error
+
+$ javac  broken/NonExhaustive.java     (21.0.12.1)
+broken/NonExhaustive.java:6: error: the switch expression does not cover all possible input values
+    static String f(S s) { return switch (s) { case A a -> "a"; }; }
+                                  ^
+1 error
+
+$ javac  broken/DominatedCase.java     (21.0.12.1)
+broken/DominatedCase.java:3: error: this case label is dominated by a preceding case label
+    static String f(Object o) { return switch (o) { case CharSequence cs -> "cs"; case String s -> "s"; default -> "d"; }; }
+                                                                                       ^
+1 error