@Override
	public Long get(Address addr) {
		validate(lock);
		Table table = propertyTable;
		if (table == null) {
			return null;
		}
		long addrKey = addrMap.getKey(addr, false);
		if (addrKey == AddressMap.INVALID_ADDRESS_KEY) {
			return null;
		}
		return cache.computeIfAbsent(addrKey, valueReader);
	}
Construct a long property map.
@param dbHandle database handle.
@param openMode the mode that the program was openned in or null if instantiated during
cache invalidate.  Used to detect versioning error only.
@param errHandler database error handler.
@param changeMgr change manager for event notification	 
@param addrMap address map.
@param name property name.
@param monitor progress monitor that is only used when upgrading
@throws VersionException if the database version is not the expected version.
@throws CancelledException if the user cancels the upgrade operation.
@throws IOException if a database io error occurs.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/properties/LongPropertyMapDB.java