JDK Command Line Tools https://tinyurl.com/java-cli-tools

jdk-cli-tools.sh

# english output for tools
export JAVA_TOOL_OPTIONS=-Duser.language=en

# sdkman
sdk list
sdk list java
#sdk install java 20-open
sdk use java 20-open
java -version

# jshell
jshell --enable-preview

System.out.println("Hello Devoxx UK!")

IntStream.range(1,10).map(i -> i*i).filter(i -> i%2==0).toArray()

var threads = 
IntStream.range(0,10).mapToObj(i -> 
		Thread.ofVirtual().start(() -> {
System.out.println("Hello Virtual Thread "+i+" "+Thread.currentThread());
})).toList();
for (Thread t : threads) {
  t.join();
}

# Game of Life in jshell

// GOL Rules: Cell is alive, if it was alive and has 2 or 3 
// living neighbours or always with 3 living neighbours
import static java.util.stream.IntStream.range;
import static java.util.stream.Collectors.*;
import static java.util.function.Predicate.*;

record Cell(int x, int y) {
   Stream<Cell> nb() {
       return range(x()-1,x()+2)
         .mapToObj(i -> i)
         .flatMap(x -> range(y()-1,y()+2)
         .mapToObj(y -> new Cell(x,y)))
         .filter(c -> !this.equals(c));
   }
   boolean alive(Set<Cell> cells) {
       var count = nb().filter(cells::contains).count();
       return (cells.contains(this) && count == 2) || count == 3;
   }
}
Set<Cell> evolve(Set<Cell> cells) {
    return cells.stream().flatMap(c -> c.nb()).distinct()
    .filter(c -> c.alive(cells))
    .collect(toSet());
}
void print(Set<Cell> cells) {
    var min=new Cell(cells.stream().mapToInt(Cell::x).min().getAsInt(),
                     cells.stream().mapToInt(Cell::y).min().getAsInt());
    var max=new Cell(cells.stream().mapToInt(Cell::x).max().getAsInt(),
                     cells.stream().mapToInt(Cell::y).max().getAsInt());
    range(min.y(), max.y()+1)
    .mapToObj(y -> range(min.x(), max.x()+1)
    .mapToObj(x -> cells.contains(new Cell(x,y)) ? "X" : " ")
    .collect(joining(""))).forEach(System.out::println);
}
var cells = Set.of(new Cell(0,1), new Cell(1,0), new Cell(1,1),new Cell(1,2),new Cell(2,1));

void gen(Set<Cell> cells, int steps) {
    print(cells);
    if (steps>0) gen(evolve(cells),steps-1);
}

gen(cells, 10)


# java execution

# java source execution

cat > Hello.java <<EOF
public class Hello {
    public static void main(String...args) {
        System.out.println("Hello "+String.join(" ",args)+"!");
    }
}
EOF

java Hello.java
cp Hello.java hello
chmod +x hello
vi hello
#!/usr/bin/java --source 20

./hello London

# jbang

jbang init -t cli hellocli.java
jbang hellocli.java
./hellocli.java --help
jbang edit hellocli.java
jbang hellocli.java London

# jwebserver

jwebserver -d `pwd`

# jps

jps
jps -l
jps -q
jps -m

# jstack

jstack 36612
jstack -h
kill -3 36612

# jcmd

jcmd 36612
jcmd 36612 GC.run
jcmd 36612 VM.info

jps

jcmd EnterpriseEntryPoint $'VM.version\nVM.uptime\nVM.flags'

jcmd EnterpriseEntryPoint GC.heap_info
jcmd EnterpriseEntryPoint GC.class_histogram | head

jbang NeoTest.java --requests 10000 --query "RETURN 1"
jbang NeoTest.java --requests 10000 --query "MATCH path=(:Person)-->() RETURN path LIMIT 5"
jbang NeoTest.java --requests 10000 --query "MATCH () RETURN count(*)" --concurrency 6

jcmd EnterpriseEntryPoint JFR.start name=neo
jcmd EnterpriseEntryPoint JFR.dump name=neo filename=/tmp/my_recording.jfr
jcmd EnterpriseEntryPoint JFR.stop name=neo
jfr summary /tmp/my_recording.jfr | head -20

# async-profiler

./async-profiler-2.8.3-macos/profiler.sh 36612 -d 15 -f /tmp/flamegraph.html

open /tmp/flamegraph.html -a "Arc"

# jlink

java --list-modules
jlink \
--add-modules java.base \
--output ./jdk-base  

./jdk-base/bin/java --list-modules
du -sh jdk-base

jdeps -s hello.jar
jdeps -s 
rm -rf jdk-base
jlink \
--add-modules java.base \
--compress 2 --output ./jdk-base
du -sh jdk-base

# javac -d target module-info.java
# javac -d target --module-path target HttpEcho.java
# java --module-path target --module httpEchoModule/de.jexp.jlink.HttpEcho
jdeps --module-path /Users/mh/d/java/javaspektrum/jlink/target -s --module httpEchoModule


# jdeprscan

jdeprscan --release 20 neo4j-kernel-5.7.0.jar 2>&1 | grep -v "cannot"