Making a Class Threadsafe using Inheritance

Question

Suppose I have a class like this:

package com.spotonsystems.bulkadmin.cognosSDK.util.Logging;

public class RecordLogging implements LittleLogging{

    private LinkedList <String> logs;
    private boolean startNew;

    public RecordLogging() {
        logs = new LinkedList<String>();
    }

    public void log(String log) {
        logHelper(log);
        startNew = true;
    }

    public void logPart(String log) {
        logHelper(log);
        startNew = false;
    }

    private void logHelper(String log){
        // DO STUFF
    }

    public LinkedList<String> getResults() {
        return logs;
    }

}

Now suppose that I need a thread safe version of this code. I need the tread safe version to implement LittleLogging. I want the thread safe copy to have the same behavior as this class except I would like it to be thread safe. Is it safe to do this:

package com.spotonsystems.bulkadmin.cognosSDK.util.Logging;

public class SyncRecordLogging extends RecordLogging {

    public SyncRecordLoging() {
        super();
    }

    public syncronized void log(String log) {
        super.log(log);
    }

    public syncronized void logPart(String log) {
        super.log(log);
    }

    public syncronized LinkedList<String> getResults() {
        return logs;
    }
}

Bonus Question: Where should I look for documentation about syncronization and threading

You know, not everything needs to use inheritance. Try a little composition from time to time to mix things up. ;) — Marvo
– Marvo, Commented Aug 8, 2011 at 19:53

Dmitry · Accepted Answer · 2011-08-08 20:42:16Z

3

You can use composition instead. Also note that getResults creates a copy of the list:

public class SyncRecordLogging  implements LittleLogging{

    private final RecordLogging _log;

    public SyncRecordLogging() {
        _log = new RecordLogging();
    }

    public synchronized void log(String log) {
        _log.log(log);
    }

    public synchronized void logPart(String log) {
        _log.logPart(log);
    }

    public synchronized LinkedList<String> getResults() {
        // returning copy to avoid 'leaking' the enderlying reference
        return new LinkedList(_log.getResults());
    }
}

Best read: Java Concurrency In Practice

edited Aug 8, 2011 at 20:42

answered Aug 8, 2011 at 20:36

Dmitry

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2 Comments

sixtyfootersdude Over a year ago

I think that I would not need to include logHelper for this case.

Dmitry Over a year ago

@sixtyfootersdude: Correct, removed from answer.

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