public class ThreadSafeLazySupplier<T> implements Supplier<T> {
    private final Supplier<T> factory;
    private final Object valueCreationMonitor;
    private volatile boolean hasValue;
    private volatile T value;
    
    public ThreadSafeLazySupplier(final Supplier<T> factory) {
        this.factory = factory;
        valueCreationMonitor = new Object();
        hasValue = false;
    }
    
    @Override
    public T get() {
        if (!hasValue) {
            synchronized(valueCreationMonitor) {
                if (!hasValue) {
                    value = factory.get();
                    hasValue = true;
                }
            }
        }
        
        return value;
    }
}