OK task 2

OffMap.java

interface OffMap {

    long get();

    void close();

}

class Wrap implements OffMap {

    private final OffMap map;
    private volatile boolean closed = false;
    private final ReadWriteLock lock = new ReentrantReadWriteLock();

    public Wrap(OffMap map) {
        this.map = map;
    }

    @Override
    public long get() {
        Lock readLock = this.lock.readLock();
        readLock.lock();
        try {
            if (closed) {
                throw new UnsupportedOperationException("Already closed");
            }
            return map.get();
        } finally {
            readLock.unlock();
        }
    }

    @Override
    public void close() {
        Lock writeLock = this.lock.writeLock();
        writeLock.lock();
        try {
            if (closed) {
                return;
            }
            closed = true;
            map.close();
        } finally {
            writeLock.unlock();
        }
    }

}

OffMap это какой-то тяжёлый ресурс. Надо его аккуратно синхронизировать