Stateful Goroutines in Squirrel

This example demonstrates how to manage state using concurrent operations in Java. While Java doesn’t have built-in concepts like goroutines and channels, we can achieve similar functionality using threads and concurrent data structures.

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;
import java.util.Random;

class ReadOperation {
    int key;
    int result;
}

class WriteOperation {
    int key;
    int value;
}

public class StatefulThreads {
    public static void main(String[] args) throws InterruptedException {
        AtomicLong readOps = new AtomicLong();
        AtomicLong writeOps = new AtomicLong();

        Map<Integer, Integer> state = new ConcurrentHashMap<>();
        Random random = new Random();

        // This thread manages the state
        Thread stateManager = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(1); // Simulate some work
                } catch (InterruptedException e) {
                    break;
                }
            }
        });
        stateManager.start();

        // Start 100 read threads
        for (int r = 0; r < 100; r++) {
            new Thread(() -> {
                while (true) {
                    ReadOperation read = new ReadOperation();
                    read.key = random.nextInt(5);
                    read.result = state.getOrDefault(read.key, 0);
                    readOps.incrementAndGet();
                    try {
                        Thread.sleep(1);
                    } catch (InterruptedException e) {
                        break;
                    }
                }
            }).start();
        }

        // Start 10 write threads
        for (int w = 0; w < 10; w++) {
            new Thread(() -> {
                while (true) {
                    WriteOperation write = new WriteOperation();
                    write.key = random.nextInt(5);
                    write.value = random.nextInt(100);
                    state.put(write.key, write.value);
                    writeOps.incrementAndGet();
                    try {
                        Thread.sleep(1);
                    } catch (InterruptedException e) {
                        break;
                    }
                }
            }).start();
        }

        // Let the threads work for a second
        Thread.sleep(1000);

        // Capture and report the op counts
        System.out.println("readOps: " + readOps.get());
        System.out.println("writeOps: " + writeOps.get());

        System.exit(0);
    }
}

In this example, we use Java’s concurrency features to manage shared state across multiple threads:

We define ReadOperation and WriteOperation classes to encapsulate read and write requests.
We use a ConcurrentHashMap to store the state, which is thread-safe and doesn’t require explicit locking.
Instead of channels, we use the map directly for communication between threads.
We create separate threads for reads and writes, similar to the goroutines in the original example.
We use AtomicLong for counting operations, which provides atomic (thread-safe) increment operations.
The main thread sleeps for a second to allow the worker threads to run, then reports the final counts.

To run the program, compile and execute it:

$ javac StatefulThreads.java
$ java StatefulThreads
readOps: 71708
writeOps: 7177

This Java implementation achieves similar functionality to the original example, using threads instead of goroutines and a ConcurrentHashMap instead of channels for communication. The approach might be more familiar to Java developers, but it lacks some of the built-in synchronization features that Go provides with channels.

Remember that the exact number of operations may vary between runs due to the concurrent nature of the program.

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Stateful Goroutines in Squirrel