package de.vogella.concurrency.threads;

/**
 * MyRunnable will count the sum of the number from 1 to the parameter
 * countUntil and then write the result to the console.
 * 

 * MyRunnable is the task which will be performed
 *
 * @author Lars Vogel
 *
 */
public class MyRunnable implements Runnable {
    private final long countUntil;

    MyRunnable(long countUntil) {
        this.countUntil = countUntil;
    }

    @Override
    public void run() {
        long sum = 0;
        for (long i = 1; i < countUntil; i++) {
            sum += i;
        }
        System.out.println(sum);
    }
}

package de.vogella.concurrency.threads;

import java.util.ArrayList;
import java.util.List;

public class Main {

    public static void main(String[] args) {
        // We will store the threads so that we can check if they are done
        List<Thread> threads = new ArrayList<Thread>();
        // We will create 500 threads
        for (int i = 0; i < 500; i++) {
            Runnable task = new MyRunnable(10000000L + i);
            Thread worker = new Thread(task);
            // We can set the name of the thread
            worker.setName(String.valueOf(i));
            // Start the thread, never call method run() direct
            worker.start();
            // Remember the thread for later usage
            threads.add(worker);
        }
        int running = 0;
        do {
            running = 0;
            for (Thread thread : threads) {
                if (thread.isAlive()) {
                    running++;
                }
            }
            System.out.println("We have " + running + " running threads. ");
        } while (running > 0);

    }
}

package de.vogella.concurrency.threadpools;

/**
 * MyRunnable will count the sum of the number from 1 to the parameter
 * countUntil and then write the result to the console.
 * 

 * MyRunnable is the task which will be performed
 *
 * @author Lars Vogel
 *
 */
public class MyRunnable implements Runnable {
    private final long countUntil;

    MyRunnable(long countUntil) {
        this.countUntil = countUntil;
    }

    @Override
    public void run() {
        long sum = 0;
        for (long i = 1; i < countUntil; i++) {
            sum += i;
        }
        System.out.println(sum);
    }
}

package de.vogella.concurrency.threadpools;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Main {
    private static final int NTHREDS = 10;

    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(NTHREDS);
        for (int i = 0; i < 500; i++) {
            Runnable worker = new MyRunnable(10000000L + i);
            executor.execute(worker);
        }
        // This will make the executor accept no new threads
        // and finish all existing threads in the queue
        executor.shutdown();
        // Wait until all threads are finish
        executor.awaitTermination();
        System.out.println("Finished all threads");
    }
}

CompletableFuture.supplyAsync(this::doSomething);

package snippet;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;

public class CompletableFutureSimpleSnippet {
    public static void main(String[] args) {
        long started = System.currentTimeMillis();

        // configure CompletableFuture
        CompletableFuture<Integer> futureCount = createCompletableFuture();

            // continue to do other work
            System.out.println("Took " + (started - System.currentTimeMillis()) + " milliseconds" );

            // now its time to get the result
            try {
              int count = futureCount.get();
                System.out.println("CompletableFuture took " + (started - System.currentTimeMillis()) + " milliseconds" );

               System.out.println("Result " + count);
             } catch (InterruptedException | ExecutionException ex) {
                // Exceptions from the future should be handled here
            }
    }

    private static CompletableFuture<Integer> createCompletableFuture() {
        CompletableFuture<Integer> futureCount = CompletableFuture.supplyAsync(
                () -> {
                    try {
                        // simulate long running task
                        Thread.sleep(5000);
                    } catch (InterruptedException e) { }
                    return 20;
                });
        return futureCount;
    }

}

package snippet;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;

public class CompletableFutureCallback {
    public static void main(String[] args) {
        long started = System.currentTimeMillis();

        CompletableFuture<String>  data = createCompletableFuture()
                .thenApply((Integer count) -> {
                    int transformedValue = count * 10;
                    return transformedValue;
                }).thenApply(transformed -> "Finally creates a string: " + transformed);

            try {
                System.out.println(data.get());
            } catch (InterruptedException | ExecutionException e) {

            }
    }

    public static CompletableFuture<Integer> createCompletableFuture() {
        CompletableFuture<Integer>  result = CompletableFuture.supplyAsync(() -> {
            try {
                // simulate long running task
                Thread.sleep(5000);
            } catch (InterruptedException e) { }
            return 20;
        });
        return result;
    }

}

package de.vogella.concurrency.nonblocking.counter;

import java.util.concurrent.atomic.AtomicInteger;

public class Counter {
    private AtomicInteger value = new AtomicInteger();
    public int getValue(){
        return value.get();
    }
    public int increment(){
        return value.incrementAndGet();
    }

    // Alternative implementation as increment but just make the
    // implementation explicit
    public int incrementLongVersion(){
        int oldValue = value.get();
        while (!value.compareAndSet(oldValue, oldValue+1)){
             oldValue = value.get();
        }
        return oldValue+1;
    }

}

package de.vogella.concurrency.nonblocking.counter;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class Test {
        private static final int NTHREDS = 10;

        public static void main(String[] args) {
            final Counter counter = new Counter();
            List<Future<Integer>> list = new ArrayList<Future<Integer>>();

            ExecutorService executor = Executors.newFixedThreadPool(NTHREDS);
            for (int i = 0; i < 500; i++) {
                Callable<Integer> worker = new  Callable<Integer>() {
                    @Override
                    public Integer call() throws Exception {
                        int number = counter.increment();
                        System.out.println(number );
                        return number ;
                    }
                };
                Future<Integer> submit= executor.submit(worker);
                list.add(submit);

            }


            // This will make the executor accept no new threads
            // and finish all existing threads in the queue
            executor.shutdown();
            // Wait until all threads are finish
            while (!executor.isTerminated()) {
            }
            Set<Integer> set = new HashSet<Integer>();
            for (Future<Integer> future : list) {
                try {
                    set.add(future.get());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            }
            if (list.size()!=set.size()){
                throw new RuntimeException("Double-entries!!!");
            }

        }


}

public final int incrementAndGet() {
        for (;;) {
            int current = get();
            int next = current + 1;
            if (compareAndSet(current, next))
                return next;
        }
    }

package algorithm;

import java.util.Random;

/**
 *
 * This class defines a long list of integers which defines the problem we will
 * later try to solve
 *
 */
public class Problem {
    private final int[] list = new int[2000000];

    public Problem() {
        Random generator = new Random(19580427);
        for (int i = 0; i < list.length; i++) {
            list[i] = generator.nextInt(500000);
        }
    }

    public int[] getList() {
        return list;
    }

}

package algorithm;

import java.util.Arrays;

import jsr166y.forkjoin.RecursiveAction;

public class Solver extends RecursiveAction {
    private int[] list;
    public long result;

    public Solver(int[] array) {
        this.list = array;
    }

    @Override
    protected void compute() {
        if (list.length == 1) {
            result = list[0];
        } else {
            int midpoint = list.length / 2;
            int[] l1 = Arrays.copyOfRange(list, 0, midpoint);
            int[] l2 = Arrays.copyOfRange(list, midpoint, list.length);
            Solver s1 = new Solver(l1);
            Solver s2 = new Solver(l2);
            forkJoin(s1, s2);
            result = s1.result + s2.result;
        }
    }
}

package testing;

import jsr166y.forkjoin.ForkJoinExecutor;
import jsr166y.forkjoin.ForkJoinPool;
import algorithm.Problem;
import algorithm.Solver;

public class Test {

    public static void main(String[] args) {
        Problem test = new Problem();
        // check the number of available processors
        int nThreads = Runtime.getRuntime().availableProcessors();
        System.out.println(nThreads);
        Solver mfj = new Solver(test.getList());
        ForkJoinExecutor pool = new ForkJoinPool(nThreads);
        pool.invoke(mfj);
        long result = mfj.getResult();
        System.out.println("Done. Result: " + result);
        long sum = 0;
        // check if the result was ok
        for (int i = 0; i < test.getList().length; i++) {
            sum += test.getList()[i];
        }
        System.out.println("Done. Result: " + sum);
    }
}