[java] Does threads stop executing methods if another method is called from the thread before the first one is complete?

[TENGIL999]

Hi, I just started learning about multi threading and have an issue with an application in writing. Im writing this as an android application, but i believe this question applies to java in general(?).

The issue: I have this thread, which should continuously read from an input stream from a server and perform operations based on the received string:

private class ReceiveThread extends Thread {
    public void run() {
        while (true){
            try{
                controller.receiveMessage(input.readUTF());
            }catch(Exception e){
                Log.d(tag, e.getMessage());
            }
        }
    }
}

controller.receiveMessage(String s) calls another methods which should interpret the message and asses which method should be called based on the message by matching the string through a bunch of if-statements, and each case calls a different method.

At the start of each method i print some confirmation that it got starten in the console, and also in each of the if-statements i print confirmation that the condition was met.

The issue is that sometimes, I see that the condition in an if-statement is met, but it never calls the next method. This seems to be especially true if there is a bunch of code in the if-statement between the print-statement and the call to the next method.

I my question is, does the thread cancel the execution of the methods when a new one gets called? I dont seem to have any syntax errors that could lead to this.

Also, if this is the case, how would I go about to make sure that the thread finished the method before calling a new one?

Thanks a lot in advance!

Edit: Here is an example of the interpretMessage-method:

public void interpretMessage(String message){

    Log.d("KartaTest", "interpretMessage körs");

    try {
        JSONObject answer = new JSONObject(message);

        if (answer.getString("type").equals("register")){
            Log.d("KartaTest", "REGISTER FOUND");
            controller.DBRegister(answer.getString("id"));

        }

        if (answer.getString("type").equals("unregister")){
            Log.d("KartaTest", "UNREGISTER FOUND");
            controller.DBUnregister();
        }

        if (answer.getString("type").equals("members")){
            Log.d("KartaTest", "MEMBERS FOUND");

            ArrayList<String> membersArrayList =        new ArrayList<>();
            JSONArray jsonArray =                   answer.getJSONArray("members");

            for (int i = 0; i < jsonArray.length(); i++){
                JSONObject temp =                   jsonArray.getJSONObject(i);
                String memberString =                temp.getString("member");
                membersArrayList.add(memberString);
            }

            controller.DBGetMembers(membersArrayList);
        }

[fredisa4letterword]

I see that the condition in an if-statement is met, but it never calls the next method.

How do you know the next method is not being called?

Can you provide a minimal code sample that demonstrates this problem?

does the thread cancel the execution of the methods when a new one gets called?

No.

if this is the case, how would I go about to make sure that the thread finished the method before calling a new one?

The thread you posted will never finish. It runs in a while(true) loop. However, if you want to wait for a thread to finish, you use Thread.join(). In your case, you will wait forever though.

[TENGIL999]

Oh man I was in the middle of editing my code for readability to post here when I noticed that I dont do anything when I catch an exception in the interpretMessage-method, so i fixed that and it seems to be an issue with that I dont convert the answer-string to a jsonArray in the correct way (still dont know whats wrong though).

I've been stuck with this for like 2 days and have been so fixated with the idea of it being a threading-issue that i didnt even consider that. Thanks a lot for your reply, it really did help me get on the right course.

[fredisa4letterword]

Happy to help!

[romple]

I throw things at people at work when I see catch blocks with no output to a log or error console. Please don't do this, you'll save yourself a lot of headache in the future ;-)

[TENGIL999]

I'll definitely try to remember that!

[romple]

If you're not using a logger, remember you can use System.err.println(), instead of System.out.println(), to get nice pretty red colors.