execution_result.txt

Removal failed
Removal failed
Removal failed
...
Removal failed
Removal failed
Removal failed
B: 494
A: 534

ThreadTest.java

import java.util.ArrayList;
import java.util.List;
 
import org.apache.pulsar.common.util.collections.ConcurrentOpenHashMap;
 
public class ThreadTest {
 
    private static final int NUM_THREADS = 100;
    private static ConcurrentOpenHashMap<String, List<Object>> map = new ConcurrentOpenHashMap<>();
 
    private static class Updater extends Thread {
 
        private static final int NUM_TRIALS = 1000;
 
        @Override
        public void run() {
            for (int i = 0; i < NUM_TRIALS; i++) {
                String key = i % 2 == 0 ? "A" : "B";
                Object obj = new Object();
 
                if (!map.computeIfAbsent(key, k -> new ArrayList<>()).add(obj)) {
                    System.out.println("Addition failed");
                }
 
                if (map.containsKey(key)) {
                    if (!map.get(key).remove(obj)) {
                        System.out.println("Removal failed");
                    }
                } else {
                    System.out.println(key + " key is not contained");
                }
            }
        }
    }
 
    public static void main(String[] args) throws Exception {
        Updater[] threads = new Updater[NUM_THREADS];
 
        for (int i = 0; i < NUM_THREADS; i++) {
            threads[i] = new Updater();
            threads[i].start();
        }
 
        for (int i = 0; i < NUM_THREADS; i++) {
            threads[i].join();
        }
 
        for (String key : map.keys()) {
            System.out.println(key + ": " + map.get(key).size());
        }
    }
}