Java process array in parallel

Question

I have an array I want to process in different ways in parallel to speed up the overall runtime of my program. Here is what the program looks like when doing everything sequentially.

public static void main(String[] args) {
    ArrayList<MyObject> array = getLongListOfObjects();
    ArrayList<MyObject2> array2 = new ArrayList<MyObject2>();
    for(MyObject object : array) {
         array2.add(firstProcessingMethod(object);
    }
    ArrayList<MyObject3> array3 = new ArrayList<MyObject3>();
    for(MyObject2 object : array2) {
         array3.add(secondProcessingMethod(object);
    }
    ArrayList<MyObject4> array4 = new ArrayList<MyObject4>();
    for(MyObject3 object : array3) {
         array4.add(thirdProcessingMethod(object);
    }
    for(MyObject4 object : array4) {
         System.out.println(object.toString());
    }
}

In other words I want to start processing the array with firstProcessingMethod() and after the first iteration I can start running secondProcessingMethod() and thirdProcessingMethod() while the rest of the array is still going through firstProcessingMethod().

castletheperson · Accepted Answer · 2016-07-07 21:11:15Z

4

With Java 8, you can use Streams.

array.parallelStream()
    .map(ThisClass::firstProcessingMethod)
    .map(ThisClass::secondProcessingMethod)
    .map(ThisClass::thirdProcessingMethod)
    .forEach(System.out::println);

edited Jul 7, 2016 at 21:11

answered Jul 7, 2016 at 21:05

castletheperson

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2 Comments

zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz Over a year ago

What is ThisClass:: referring to?

castletheperson Over a year ago

It's referring to the class that contains those methods. It's kind of like passing a method as a parameter. For more information, see this question

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