AJP/DiSLProject2022/src-profiler/ex9/Profiler.java

package ex9;

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

public final class Profiler {
    private static final ConcurrentMap<Thread, List<String>> callLog = new ConcurrentHashMap<>();

    static {
        Runtime.getRuntime().addShutdownHook(new Thread(Profiler::print));
    }

    private Profiler() {
    }

    public static void logCall(final Thread thread, final String methodName) {
        final List<String> list = callLog.computeIfAbsent(thread, ignored -> new LinkedList<>());

        // thread safe, as once a thread accesses its own list access to said list is non-concurrent
        list.add(methodName);
    }

    private static void print() {
        for (final Thread thread : callLog.keySet()) {
            System.out.printf("=== %s ===\n", thread.getName());
            callLog.get(thread).forEach(System.out::println);
        }
    }
}