CODEWITHSUNDEEP
javajava-8java-stream
Michael
Michael

Reputation: 2773

Creating a Custom IntStream-like class

In Java 8, you can write code like the following:

List<Integer> list = IntStream
    .range(0, 100)
    .boxed()
    .collect(Collectors.toCollection(ArrayList::new));

How can I create a custom XStream class? For example, say I have a class that naturally can be ordered, and you can naturally have predecessors and successors to an object. Like:

public class PurchaseOrder {
    public long orderNumber;

    public PurchaseOrder(){
        orderNumber = 0L;
    }
}

Then, I could have a theoretical PurchaseOrderStream that you can write the following code for:

List<PurchaseOrder> list = PurchaseOrderStream
    .range(0, 100)
    .collect(Collectors.toCollection(ArrayList::new));

How could I go about doing this? Are there any classes or interfaces I need PurchaseOrderStream to extend / implement? I'm not looking for full source code (though that would be nice), but just a push in the right direction.

Upvotes: 3

Views: 376

Answers (1)

Paul Boddington
Paul Boddington

Reputation: 37645

The easiest way would just be to use the methods already available. I can't see any reason to reinvent the wheel here.

For example, if you wrote a static method PurchaseOrder getFromId(long id) you could just do

LongStream.range(0, 100).mapToObj(PurchaseOrder::getFromId)
                        .collect(Collectors.toCollection(ArrayList::new));

If this isn't short enough, you could write a method

public static Stream<PurchaseOrder> range(long low, long high) {
    return LongStream.range(low, high).mapToObj(PurchaseOrder::getFromId);
}

Then you could write

PurchaseOrder.range(0, 100).collect(Collectors.toCollection(ArrayList::new));

Upvotes: 7

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