CODEWITHSUNDEEP
javamultithreadingparallel-processing
user1037452
user1037452

Reputation: 391

How to run different methods parallely

I have one java method which contains 5 different internal methods. For performance improvement, I want to call these methods parallely.

e.g. run method1, method2, ... method5 parallel using thread.

private void getInformation() throws SQLException,
            ClassNotFoundException, NamingException {
    method1();
    method2();
    method3();
    method4();
    method5();
}

but all these 5 methods have different business logic.

Upvotes: 11

Views: 50940

Answers (6)

Carl
Carl

Reputation: 93

I had similar requirement. On a specific operation, I had to call some set of validator methods which in-turn validates certain components. Every validator used to take certain amount of time and had to reduce it and decided to call it in async.

Indeed there are many ways to achieve it, this is one of the approach which I solved.

Since validators mostly doesn't return any values, took advantage of Runnable class lambda. In below example addition, multiply and subtraction methods will be invoked asynchronously and in parallel.

public class MultiThreading {

        public static void addition() {
            System.out.println("Addition");
        }

        public static void multiply() {
            System.out.println("multiplication");
        }

        public static void subtraction() {
            System.out.println("subtraction");
        }

        public static void main(String[] args) {
            ExecutorService executor = Executors.newCachedThreadPool();

            Runnable callMultiply = () -> multiply();  //Create Runnable reference using lambda
            executor.execute(callMultiply);
            executor.execute(() -> addition()); //inline
            executor.execute(() -> subtraction());
            
            executor.shutdown();
        }
    }

Upvotes: 7

lreeder
lreeder

Reputation: 12206

Do something like this:

  1. For each method, create a Callable object that wraps that method.
  2. Create an Executor (a fixed thread pool executor should be fine).
  3. Put all your Callables in a list and invoke them with the Executor.

Here's a simple example:

public void testThread()
{

   //create a callable for each method
   Callable<Void> callable1 = new Callable<Void>()
   {
      @Override
      public Void call() throws Exception
      {
         method1();
         return null;
      }
   };

   Callable<Void> callable2 = new Callable<Void>()
   {
      @Override
      public Void call() throws Exception
      {
         method2();
         return null;
      }
   };

   Callable<Void> callable3 = new Callable<Void>()
   {
      @Override
      public Void call() throws Exception
      {
         method3();
         return null;
      }
   };

   //add to a list
   List<Callable<Void>> taskList = new ArrayList<Callable<Void>>();
   taskList.add(callable1);
   taskList.add(callable2);
   taskList.add(callable3);

   //create a pool executor with 3 threads
   ExecutorService executor = Executors.newFixedThreadPool(3);

   try
   {
      //start the threads and wait for them to finish
      executor.invokeAll(taskList);
   }
   catch (InterruptedException ie)
   {
      //do something if you care about interruption;
   }

}

private void method1()
{
   System.out.println("method1");
}

private void method2()
{
   System.out.println("method2");
}

private void method3()
{
   System.out.println("method3");
}

Make sure each method does not share state (like a common mutable field in the same class) or you may get unexpected results. Oracle provides a good introduction to Java Executors. Also, this book is awesome if you are doing any kind of threading in java.

Upvotes: 21

Alexei Kaigorodov
Alexei Kaigorodov

Reputation: 13515

To run method1 in parallel, do following:

Thread t1=new Thread() {
   public void run() {
       method1();
   }
};
t1.start();

Do this for all your methods.

To wait method1 to finish, do 

t1.join();

and so for all other threads.

Many people will tell you use threadpool and do not extend Thread - all this has little sense for you just now. Master this way and only then follow that advices.

Upvotes: 5

pditommaso
pditommaso

Reputation: 3381

You have to use 5 different threads to execute your methods in parallel, the code it's not difficult but pretty boring.

You may want to have a look to Gpars Tasks, which make writing parallel code much more easy and enjoyable.

http://gpars.org/1.0.0/guide/guide/dataflow.html#dataflow_tasks

Upvotes: 0

jlb
jlb

Reputation: 357

take a look at java.util.concurrent http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/package-summary.html and the tutorial: http://docs.oracle.com/javase/tutorial/essential/concurrency/ basically, you will have to create an executorserice, some class extending Runnable, and invoke them

Upvotes: 0

XZen
XZen

Reputation: 445

You can use high level concurrency instrument in Java - thread pool. But anyway you will have to create Runnable objects (tasks) and then use thread pool's method - invokeAll(). Please take a look at Oracle concurrency tutorial

Upvotes: 0

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