Java 8 Lambda - Intersection of Two Lists

Question

I am trying to find intersection of two lists based on some condition and doing some steps. Couldn't find a way to do it (in learning stage) :)

Double totalAmount = 0.00d;
Double discount = 0.00d;


List<OrderLineEntry> orderLineEntryList = orderEntry.getOrderReleases().stream()
    .flatMap(orderReleaseEntry -> orderReleaseEntry.getOrderLines().stream())
    .filter(orderLineEntry -> orderLineEntry.getStatus().equals("PP") || orderLineEntry.getStatus().equals("PD"))
    .collect(Collectors.toList());

for (OrderLineEntry orderLineEntry : orderLineEntryList) {
    for (SplitLineEntry splitLineEntry : splitReleaseEntry.getLineEntries()) {
        if (splitLineEntry.getOrderLineId().equals(orderLineEntry.getId()) && splitLineEntry.getStatusCode() != "PX") {
            totalAmount += orderLineEntry.getFinalAmount();
            couponDiscount += orderLineEntry.getCouponDiscount() == null ? 0.00d : orderLineEntry.getCouponDiscount();
        }
    }
}

As you see, the logic is simple

Get All items from order based on some filter list and intersect with another list and do some stuff.

Answer 1

The simplest approach is this:

List<T> intersect = list1.stream()
                         .filter(list2::contains)
                         .collect(Collectors.toList());