How to Call Methods Simultaneously in Java

How can I call methods simultaneously in Java?

Make use of multiple threads, although you should read up on concurrency if you're going to edit the same objects from multiple threads.

public static void main(String[] args) {
    new Thread() { 
        public void run() {
            method1();
        }
    }.start();
    new Thread() { 
        public void run() {
            method2();
        }
    }.start();
    //etc

    //or, as kingdamian42 pointed out, if you use java8, use this
    new Thread(() -> method1()).start();
    new Thread(() -> method2()).start();
}

how to call methods in java simultaneously?

Don't conflate game time with CPU time. Just because players move at the same game time doesn't mean you need to have CPU threads executing concurrently. You just need a logic loop that simulates simultaneous movement.

For example, loop over all the players and check that their actions don't conflict with each other. If two players want to move to the same location, show an error. Otherwise, loop over them a second time and move them all to their new locations. Then redraw the scene. Even though you're updating the players one at a time in the second loop, the screen won't show the movements until the entire scene is repainted.

How to run 2 methods concurrently in same class with Java

There are several ways to achieve your task. You have quiet easy situation when threads should not be synchronized.

You can use ExecutorService from Java Concurrency:

public class ConcurrentCode {
    
    private int countA = 0;
    private int countB = 0;
    
    int countA(){
        for (int i = 0; i < 1000; i++) {
            countA++;
        }
        System.out.println(countA);
        return countA;
    }
    
    int countB(){
        for (int i = 0; i < 1000; i++) {
            countB++;
        }
        System.out.println(countB);
        return countB;
    }
    
    public void execute(){
        ExecutorService executorService = Executors.newFixedThreadPool(2);
    
        // method reference introduced in Java 8
        executorService.submit(this::countA);
        executorService.submit(this::countB);
    
        // close executorService
        executorService.shutdown();
    }
    
    
    public static void main(String[] args){
        new ConcurrentCode().execute();
    }
    
}

Remember to shutdown ExecutorService otherwise your application won't stop because it will have alive threads.

Or you can have the simplest approach using vanilla Java threads:

public void executeInNativeThreads(){
    
    // starts new thread and executes countA in it
    new Thread(this::countA).start();

    // starts new thread and executes countB in it
    new Thread(this::countB).start();
    
}

To get computation results you can get the Future<Integer> from executorService and then you have a choice:

• poll Future if it is done
• wait until the Future will be completed.
• wait explicitly for a certain timeout

Here is an example:

public void execute() throws Exception {
    ExecutorService executorService = Executors.newFixedThreadPool(2);

    Future<Integer> future1 = executorService.submit(this::countA);
    Future<Integer> future2 = executorService.submit(this::countB);

    // wait until result will be ready
    Integer result1 = future1.get();

    // wait only certain timeout otherwise throw an exception
    Integer result2 = future2.get(1, TimeUnit.SECONDS);

    System.out.println("result1 = " + result1);
    System.out.println("result2 = " + result2);

    executorService.shutdown();
}

Note, while we are explicitly waiting for result of future1, future2 is still being executed in another thread. It means that there won't be big delay in computation of future2 in particularly this example.

Also, take a look at CompletionStage which is used in asynchronous computations.

How to execute the same method concurrently in Java

If you want call method concurrently you need threads. Java documentation for concurrency: https://docs.oracle.com/javase/tutorial/essential/concurrency/index.html.

You have many options how to create/use threads in java.

1)
if you know how many threads do you need you can create threads manually like this:

Thread thread1 = new Thread(()->deleteVm("a","b");
Thread thread2 = new Thread(()->deleteVm("c","d");

//START the threads
thread1.start();
thread2.start();

2)
you can use default threads pool(usually thread per cpu core) like this:

CompletableFuture.runAsync(() -> deleteVm("a", "b"));
CompletableFuture.runAsync(() -> deleteVm("c", "d"));

3)
you can create your own thread executor like this

ScheduledExecutorService executorService = Executors.nScheduledExecutorService executorService = Executors.newFixedThreadPool(5)

executorService.submit(() -> deleteVm("a", "b"));
executorService.submit(() -> deleteVm("c", "d"));

How to call multiple methods at same time?

In order to run all three methods concurrently you can use Executor to run concurrent threads, and wait for the result thanks to Future. Something like:

Executor executor = Executors.newFixedThreadPool(3);
Future<List<Student>> studentsFuture = executor.submit(() -> return studentMao.getAll(collegeId));
Future<List<Department>> departmentsFuture = executor.submit(() -> return departmentsMao.getByCollegeId(collegeId));
Future<List<College>> collegesFuture = executor.submit(() -> return collegeMao.getByUniversityId(universityId));

List<Student> students = studentsFuture.get();
List<Department> departments = departmentsFuture.get();
List<College> colleges = collegesFuture.get();

Get waits until the current task running in another threads finishes, so this piece of code will finish when all the concurrent threads have finished.

how to call a method with multiple threads

if you need simultaneous execution and each time new thread you can find the solution here

public class SleepClass {
    public static void main(String[] args) {
        SleepClass s= new SleepClass();
        s.m2(500);
        s.m2(1000);
    }
    
    public void m2(int time) {
        SleepClass s= new SleepClass();
        new Thread(() -> {
            s.m1(time);
        }).start();
    }
    
    public void m1(int time) {
        
        for(int i = 0; i<= 10; i++) {
            System.out.println(i);
            try {
                Thread.sleep(time);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        
    }

}

Spring boot execute 2 methods simultaneously

If you make your search methods async, either using thread executors pool, or @Async, you will be able to invoke them at once, and gather results after finish.

Just remember, that you will have to use Future for this.

So something like this will be

@Async
public Future<List<Whatever>> search(whatever here){
      resultList=whateverYouDoThere();
      return new AsyncResult<Whatever>(resultList);   
}

in both services ofc, and invocations:

   List<Whatever> completeList=new ArrayList():
   Future<Whatever> fut1=service1.search(...);
   Future<Whateva> fut2=service2.search(...);
   completeList.addAll(fut1.get());
   completeList.addAll(fut2.get();
    //here you got all the stuff in completeList

I skipped your case here as I was too lazy to read it carefuly, so in your case it would be

Future<SearchResult1> fut1=service1.search(params);

Future<SerchResult2> fut2 = service2.search(params);

model.addAttribute("list1", fut1.get());

model.addAttribute("list2", fut2.get());

or something very similar

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