kabutz

/** In memory of @crazybob, who loved puzzles like this. */
public class OverridingFinalToStringPuzzle {
    private static class Bull {
        public final String toString() {
            return "Bull";
        }
    }

    public static String convert(Bull bull) {
        return "%s".formatted(bull);

kabutz

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class StreamMapInvertingCompilerBug {
  public static void main(String... args) {
    Map<Integer, Long> numberCount =
        Stream.of(1, 4, 2, 5, 3, 5, 1, 3, 5, 3, 2, 1, 4, 5)
            .collect(Collectors.groupingBy(
                Function.identity(),

kabutz

package richardstartin;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OperationsPerInvocation;
import org.openjdk.jmh.annotations.OutputTimeUnit;

kabutz

package richardstartin;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OperationsPerInvocation;
import org.openjdk.jmh.annotations.OutputTimeUnit;

kabutz

// run with java -showversion CleanerDemo in Java 16 and 17 to see different results
import java.lang.ref.*;

public class CleanerDemo {
    public static void main(String... args) throws InterruptedException {
        Cleaner cleaner = Cleaner.create();
        Cleaner.Cleanable cleanable = cleaner.register(new Object(),
                () -> System.out.println("My cleaner thread priority is " +
                        Thread.currentThread().getPriority()));
        System.gc();

kabutz

package benchmarks;

import org.openjdk.jmh.annotations.*;

import java.util.*;
import java.util.concurrent.*;

@Fork(value = 1)
@Warmup(iterations = 5, time = 3)
@Measurement(iterations = 10, time = 3)

kabutz

import java.util.concurrent.atomic.AtomicBoolean
import kotlin.concurrent.thread
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

fun atomicBoolean(default: Boolean = false) =
    object : ReadWriteProperty<Any?, Boolean> {
        val storage = AtomicBoolean(default)
        override fun getValue(thisRef: Any?, property: KProperty<*>) =
            storage.get()

kabutz

// Compile and run in Java 9.  Then compile and run in Java 8 and 9.  Enjoy your new JDK :-D
public class Java9AtLast {
  public static void hiphip(int cheers) {
    try {
      hiphip(cheers + 1);
    } catch(StackOverflowError er) {
      System.out.println("hooray x " + cheers);
    }
  }
  public static void main(String... args) {

kabutz

/**
 * As seen on https://javaspecialists.slack.com/messages/general 
 *
 * This class fails to compile with JDK 1.6, 1.7 and 1.8:
 *
 * class Two extends Observable {	// Nothing special about the choice of Observable here
 *                   ^
 *   symbol: class Observable
 * 1 error
 *

kabutz

abstract class Brick {
  public Brick() {
    greet();
  }

  public abstract void greet();
}

public class HardPlace {
  public class Between extends Brick {