Share limited amount of resources between different threads

I write selenium tests and make it parallel via testng. There are some tests which should use resource, and that resource cant be used in tests, while it using in another test. So to make it clear let me describe in other words, I have 10 resources, and when some test start working with one of them, only 9 another resources should be available in another tests. If all 10 resources are busy, and another test attempts to get it, it should wait until one of test will finish execution and free it's resource. Im trying to create provider which will control desired behaviour but it looks like I get deadlocks, because it hangs out some times at synchronized method call. My plan is provider have 2 methods get() and remove()

• get() called in test method to get resource
• remove() called in method annotated with @AfterMethod annotation and this method is default method of specific interface which should be implemented in class, containing resource usage

Here is provider class:

public class ResourceProvider {
private static final Logger logger = LogManager.getLogger();
private static List<Resource> freeResources;
private static Map<String, List<Resource>> resourcesInUse;

static {
    freeResources = new ArrayList<>();
    //here is resource initialization to fill freeResources list
    resourcesInUse = new HashMap<>();
}

public static synchronized Resource get() {
    String testName = Thread.currentThread().getStackTrace()[2].getClassName()
            + "." + Thread.currentThread().getStackTrace()[2].getMethodName();
    Resource resource = null;
    logger.info(String.format("Attempt to get resource for %s test", testName));

    for (int i = 0; i < 240; i++) {
        if (freeResources.isEmpty()) {
            try {
                Thread.sleep(5_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        } else {
            resource = freeResources.get(0);

            if (resourcesInUse.containsKey(testName)) {
                resourcesInUse.get(testName).add(resource);
            } else {
                List<Resource> resources = new ArrayList<>();
                resources.add(resource);
                resourcesInUse.put(testName, resources);
            }

            freeResources.remove(resource);
            break;
        }
    }
    if (resource == null) {
        throw new RuntimeException(String.format("There is no free resource for '%s' in 20 minutes", testName));
    }
    logger.info(String.format("Resource %s used in %s", resource, testName));
    return resource;
}

public static synchronized boolean remove(ITestResult result) {
    String testName = result.getMethod().getTestClass().getName() + "." + result.getMethod().getMethodName();
    return remove(testName);
}

public static synchronized boolean remove(String testName) {
    boolean isTestUseResource = resourcesInUse.containsKey(testName);
    if (isTestUseResource) {
        logger.info(String.format("Removing %s resources, used in %s", resourcesInUse.get(testName), testName));
        freeResources.addAll(resourcesInUse.get(testName));
        resourcesInUse.remove(testName);
    }
    return isTestUseResource;
}

Interface:

public interface RemoveResource {

@AfterMethod
default void removeResource(ITestResult result) {
    ResourceProvider.remove(result);
}

But this code doesnt work good, it hangs out at remove() call sometimes. May you help me to understand why I get hangs out and how to resolve it?