Question

I have the following class for a Router’s table with synchronised methods:

public class RouterTable {

    private String tableForRouter;
    private Map<String,RouterTableEntry> table;

    public RouterTable(String router){

        tableForRouter = router;
        table = new HashMap<String,RouterTableEntry>();
    }

    public String owner(){

        return tableForRouter;
    }

    public synchronized void add(String network, String ipAddress, int distance){

        table.put(network, new RouterTableEntry(ipAddress, distance));
    }

    public synchronized boolean exists(String network){

        return table.containsKey(network);
    }
}

Multiple threads will read and write to the HashMap. I was wondering if it would be best to remove the synchronized on the methods and just use Collections.synchronizedMap(new HashMap<String,RouterTableEntry())` what is the most sensible way in Java to do this?

Answer 1

I would suggest using a ConcurrentHashmap. This is a newer data structure introduced in later version of Java. It provides thread safety and allows concurrent operations, as opposed to a synchronized map, which will do one operation at a time.

If the map is the only place where thread safety is required, then just using the ConcurrentHashmap is fine. However, if you have atomic operations involving more state variables, I would suggest using synchronized code blocks instead of synchronized functions