How to check if a thread holds a monitor of a specific resource?

In Java, there is no direct public API to check whether the current thread holds a monitor of a specific object. However, you can use a private method of the Thread class or work around it via JMX.

Check using JMX:

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadInfo;
import java.lang.management.ThreadMXBean;

// Get access to the MBean managing threads
ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();

// Get information about all threads
ThreadInfo[] threadInfos = threadMXBean.dumpAllThreads(true, true);

// Find information about the current thread
long currentThreadId = Thread.currentThread().getId();
for (ThreadInfo threadInfo : threadInfos) {
    if (threadInfo.getThreadId() == currentThreadId) {
        // Get list of objects whose monitors are held by the thread
        ThreadInfo.LockedSynchronizer[] lockedSynchronizers = threadInfo.getLockedSynchronizers();
        for (ThreadInfo.LockedSynchronizer lockedSynchronizer : lockedSynchronizers) {
            // Compare the object ID with the resource's ID
            // (here you need to get the resource's ID, for example, its hash code)
            // if (lockedSynchronizer.getIdentityHashCode() == resource.hashCode()) {
            //     System.out.println("Thread holds the resource's monitor");
            //     break;
            // }
        }
        break;
    }
}