Consider following object:
class Interval {
final String name;
final Date start;
final Date end;
final int intervalId;
}
I am provided with a list of intervals. I need to check it equals a given map.
eg:
boolean checkEqual(List<Interval> intervals, Map<Date, Date> startEnd) {
}
I want to use Java8 to convert list of intervals into a map of start/end dates and then compare with startEndMap
i.e.
boolean checkEqual(List<Interval> intervals, Map<Date, Date> startEnd) {
Map<Date, Date> map = intervals.streams.filter ?? is there a way to do it ?
return map.equals(startEnd)
}
How to do it ?
Is there a better way ?
use the toMap collector:
Map<Date, Date> result = intervals.stream()
.collect(Collectors.toMap(Interval::getStartDate,
Interval::getEndDate));
Related
I receive a List of MediaDTO and this Object has two attributes:
String sizeType and String URL.
In 'sizeType' comes the image´s size: small, medium, large, and thumbnail.
So I have to filter the sizeType of these objects and create 4 new lists based on them.
This is how I get the List<MediaDTO> mediaDTO:
medias=[MediaDTO(sizeType=THUMBNAIL, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/thumbnail/celular-iphone-11-azul.png), MediaDTO(sizeType=SMALL, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/small/celular-iphone-11-azul.png), MediaDTO(sizeType=SMALL, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/medium/celular-iphone-11-azul.png), MediaDTO(sizeType=LARGE, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/large/celular-iphone-11-azul.png), MediaDTO(sizeType=THUMBNAIL, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/thumbnail/celular-iphone-11-vermelho.png), MediaDTO(sizeType=SMALL, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/small/celular-iphone-11-vermelho.png), MediaDTO(sizeType=MEDIUM, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/medium/celular-iphone-11-vermelho.png), MediaDTO(sizeType=LARGE, liveloUrl=https://s3.sao01.cloud-object-storage.appdomain.cloud/catalog-media-storage/id-source/productId/skuseller2/large/celular-iphone-11-vermelho.png)]
I achieved filtering for one of the sizes. This works!
However, I could not figure out how can I filter over the 4 sizes and create 4 new lists of it.
If I fix some error another appears ... so I´m really stuck.
And by the way I´ve been searching for a solution on the internet and in the forum for a couple of days but did´nt find something that fits.
If someone might help, I´d really be grateful.
I was thinking about using a 'forEach' to filter but even like that, I could filter just one size.
Thanks in advance.
**This is what I got till now: **
public class ProcessProductDTO {
String processId;
OperationProcess operation;
String categoryId;
ProductDTO productDTO;
}
public class ProductDTO {
String id;
Boolean active;
String displayName;
String longDescription;
List<MediaDTO> medias;
List<AttributeDTO> attributes;
}
public class MediaDTO {
String sizeType;
String liveloUrl;
}
public Properties toOccProductPropertiesDTO(ProcessProductDTO processProductDTO) throws JsonProcessingException {
String pSpecs = convertAttributes(processProductDTO.getProductDTO().getAttributes());
//List<String> medias = convertMedias(processProductDTO.getProductDTO().getMedias());
return Properties.builder()
.id(processProductDTO.getProductDTO().getId()) .active(processProductDTO.getProductDTO().getActive())
.listPrices(new HashMap())
.p_specs(pSpecs)
//.medias(medias)
.displayName(processProductDTO.getProductDTO()
.getDisplayName())
.longDescription(processProductDTO.getProductDTO().getLongDescription())
.build(); }
private String convertAttributes(List<AttributeDTO> attributes) throws JsonProcessingException {
Map<String, String> attribs = attributes.stream()
.collect(Collectors.toMap(AttributeDTO::getName, AttributeDTO::getValue));
return objectMapper.writeValueAsString(attribs);
}
private List<MediaDTO> convertMedias(ProcessProductDTO processProduct, List<MediaDTO> mediaDTO){
List<MediaDTO> filteredList = processProduct.getProductDTO().getMedias();
Set<String> filterSet = mediaDTO.stream().map(MediaDTO::getSizeType).collect(Collectors.toSet());
return filteredList.stream().filter(url -> filterSet.contains("SMALL")).collect(Collectors.toList());
}
UPDATE
I got the following result:
private Properties toOccProductPropertiesDTO(ProcessProductDTO processProductDTO) throws JsonProcessingException {
String pSpecs = convertAttributes(processProductDTO.getProductDTO().getAttributes());
MediaOccDTO medias = convertMedias(processProductDTO.getProductDTO().getMedias());
return Properties.builder()
.id(processProductDTO.getProductDTO().getId())
.active(processProductDTO.getProductDTO().getActive())
.listPrices(new HashMap())
.p_specs(pSpecs)
.medias(medias)
.displayName(processProductDTO.getProductDTO().getDisplayName())
.longDescription(processProductDTO.getProductDTO().getLongDescription())
.build();
}
private MediaOccDTO convertMedias(List<MediaDTO> mediaDTOs){
String smallImageUrls = generateOccUrl(mediaDTOs, ImageSizeType.SMALL);
String mediumImageUrls = generateOccUrl(mediaDTOs, ImageSizeType.MEDIUM);
String largeImageUrls = generateOccUrl(mediaDTOs, ImageSizeType.LARGE);
String thumbImageUrls = generateOccUrl(mediaDTOs, ImageSizeType.THUMB);
return MediaOccDTO.builder()
.p_smallImageUrls(smallImageUrls)
.p_mediumImageUrls(mediumImageUrls)
.p_largeImageUrls(largeImageUrls)
.p_thumbImageUrls(thumbImageUrls)
.build();
}
private String generateOccUrl(List<MediaDTO> mediaDTOs, ImageSizeType imageSizeType){
return mediaDTOs.stream()
.filter(m -> m.getSizeType().equals(imageSizeType))
.map(MediaDTO::getLiveloUrl)
.reduce(",", String::concat);
}
The problem is:
the comparison: m.getSizeType().equals(imageSizeType)
is always false, so the list gets created empty...
Though the question is laborious, I could think of the requirement being, you need to create 4 new lists based on sizeType.
Stream collector, can collect the results to a single data structure. It can be a list, set, Map etc.
Since you need 4 lists based on sizeType, you will need to pass through the stream 4 times to create 4 lists.
Another Alternate will be to create a Map<SizeType, List<MediaDTO>>
This can be achieved through,
mediaDTO.stream().collect(Collectors.toMap(i -> i.getSizeType(), i->i)
I think the toMap doesn't collect the values in a list. We need groupingBy instead.
mediaDTO.stream()
.collect(Collectors.groupingBy(MediaDTO::getSizeType));
I have the below class:
class A{
String property1;
String property2;
Double property3;
Double property4;
}
So the property1 and property2 is the key.
class Key{
String property1;
String property2;
}
I already have a list of A like below:
List<A> list=new ArrayList<>();
I want to group by using the key and add to another list of A in order to avoid having multiple items with same key in the list:
Function<A, Key> keyFunction= r-> Key.valueOf(r.getProperty1(), r.getProperty2());
But then while doing group by I have to take a sum of property3 and average of property4.
I need an efficient way to do it.
Note: I have skipped the methods of the given classes.
Collecting to a Map is unavoidable since you want to group things. A brute-force way to do that would be :
yourListOfA
.stream()
.collect(Collectors.groupingBy(
x -> new Key(x.getProperty1(), x.getProperty2()),
Collectors.collectingAndThen(Collectors.toList(),
list -> {
double first = list.stream().mapToDouble(A::getProperty3).sum();
// or any other default
double second = list.stream().mapToDouble(A::getProperty4).average().orElse(0D);
A a = list.get(0);
return new A(a.getProperty1(), a.getProperty2(), first, second);
})))
.values();
This could be slightly improved for example in the Collectors.collectingAndThen to only iterate the List once, for that a custom collector would be required. Not that complicated to write one...
Try like this:
Map<A,List<A>> map = aList
.stream()
.collect(Collectors
.groupingBy(item->new A(item.property1,item.property2)));
List<A> result= map.entrySet().stream()
.map(list->new A(list.getValue().get(0).property1,list.getValue().get(0).property1)
.avgProperty4(list.getValue())
.sumProperty3(list.getValue()))
.collect(Collectors.toList());
and create avgProperty4 and sumProperty3 methods like to this
public A sumProperty3(List<A> a){
this.property3 = a.stream().mapToDouble(A::getProperty3).sum();
return this;
}
public A avgProperty4(List<A> a){
this.property4 = a.stream().mapToDouble(A::getProperty4).average().getAsDouble();
return this;
}
result = aList.stream().collect(Collectors
.groupingBy(item -> new A(item.property1, item.property2),
Collectors.collectingAndThen(Collectors.toList(), list ->
new A(list.get(0).property1, list.get(0).property1)
.avgProperty4(list).sumProperty3(list))
)
);
Consider DynamoDB's QueryApi. Through a series of (unfortunate?) hoops,
ItemCollection<QueryOutcome>>
ends up being equivalent to
Iterable<Item>
I know this because I can do:
public PuppyDog getPuppy(final String personGuid, final String name) {
final QuerySpec spec = new QuerySpec()
.withKeyConditionExpression("#d = :guid and #n = :name")
.withNameMap(new NameMap().with("#d", "guid").with("#n", "name"))
.withValueMap(new ValueMap().withString(":guid", personGuid).withString(":name", name));
return getDog(index.query(spec));
}
private PuppyDog getDog(final Iterable<Item> itemCollection) {
// http://stackoverflow.com/questions/23932061/convert-iterable-to-stream-using-java-8-jdk
return StreamSupport.stream(itemCollection.spliterator(), false)
.map(this::createDogFor)
// it would be a little weird to find more than 1, but not sure what to do if so.
.findAny().orElse(new PuppyDog());
}
But when I try to write tests in Mockito using BDDMockito:
#Test
public void canGetPuppyDogByPersonGuidAndName() {
final PuppyDog dawg = getPuppyDog();
final ArgumentCaptor<QuerySpec> captor = ArgumentCaptor.forClass(QuerySpec.class);
final ItemCollection<QueryOutcome> items = mock(ItemCollection.class);
given(query.query(captor.capture())).willReturn(items);
}
The compiler complains when I try to make items an Iterable.
Why dis?
Dis not because of BDDMockito. Dis because ItemCollection<QueryOutcome> simply can't be cast safely into
Iterable<Item>. It can be cast into Iterable<QueryOutcome> or even Iterable<? extends Item>, but not Iterable<Item>.
Otherwise you could do this:
final ItemCollection<QueryOutcome> items = mock(ItemCollection.class);
Collection<Item> yourItemCollection = items;
yourItemCollection.add(itemThatIsNotAQueryOutcome); // violating safety of items
See also:
Is List<Dog> a subclass of List<Animal>? Why aren't Java's generics implicitly polymorphic?
Why are arrays covariant but generics are invariant?
I am trying to find best way to compare Enums in Java 6.
Say, I have an ENUM of Ticket Types which can be associated with a Traveler. If there is a list of travelers, I would like to know the traveler with the highest class of travel.
I can iterate thru the list of travelers, create a Set of unique TicketTypes, Convert to List, Sort them, Return the last element as the highest. I would like to know if there is a better way to do this?
public enum TicketType {
ECONOMY_NON_REF(1,"Economy Class, Non-Refundable"),
ECONOMY_REF(2,"Economy Full Fare Refundable"),
BUSINESS(3,"Business Class"),
FIRST_CLASS(4,"First Class, Top of the world");
private String code;
private String description;
}
public class Traveler {
private TicketType ticketType;
public Traveler(TicketType ticketType) {
this.ticketType = ticketType;
}
}
#Test
public testCompareEnums{
List<Traveler> travelersGroup1 = new ArrayList<Travelers>();
travelersGroup1.add(new Traveler(TicketType.ECONOMY_REF));
travelersGroup1.add(new Traveler(TicketType.BUSINESS));
travelersGroup1.add(new Traveler(TicketType.ECONOMY_REF));
travelersGroup1.add(new Traveler(TicketType.ECONOMY_NON_REF));
//What is the best way to find the highest class passenger in travelersGroup1.
assertEquals(TicketType.BUSINESS, getHighestClassTravler(travelersGroup1));
List<Traveler> travelersGroup2 = new ArrayList<Travelers>();
travelersGroup2.add(new Traveler(TicketType.ECONOMY_REF));
travelersGroup2.add(new Traveler(TicketType.ECONOMY_NON_REF));
travelersGroup2.add(new Traveler(TicketType.ECONOMY_REF));
travelersGroup2.add(new Traveler(TicketType.ECONOMY_NON_REF));
assertEquals(TicketType.ECONOMY_REF, getHighestClassTravler(travelersGroup2));
}
private CredentialType getHighestClassTraveler(List travelers){
Set uniqueTicketTypeSet = new HashSet();
for (Traveler t: travelers) {
uniqueTicketTypeSet.add(t.getTicketType());
}
List<TicketType> uniqueTicketTypes = new ArrayList<TicketType>(uniqueTicketTypeSet);
Collections.sort(uniqueTicketTypes);
return uniqueTicketTypes.get(uniqueTicketTypes.size()-1);
}
There's a lot of problems with the code that you posted (it won't compile without fixing a lot of errors), but the easiest way is to make Traveler implement the Comparable interface, like so:
public int compareTo(Traveler other) {
return this.getTicketType().compareTo(other.getTicketType());
}
Then to find the the Traveler with the highest TicketType, you can simply do:
Collections.max(travelers);
I have a string like
String str[]={"jan2011","feb2011","jan2010,"mar2012"};
How do I sort this by Date like: jan2010,jan2011,feb2011,mar2012
thanks for advance(not to use string functions more )
Hoi:
String[] unsorted={"jan2011","feb2011","jan2010","mar2012"};
List<String> unsortedList = Arrays.asList(unsorted);
Collections.sort(unsortedList);
String[] sorted = (String[])unsortedList.toArray();
This should do...
Assuming you have version 6 at your disposal, you can use the built-in
Collections.insertionSort(datavector, comparator);
However:
you'll need to move your strings into a Vector
you'll need to provide a Comparator class for your specific needs
The Comparator class could be something along these lines:
public class DatestringComparator implements Comparator{
public int compare(String s1, String s2) {
// create Date instance based on the content of the input string
Date d1 = ....;
Date d2 = ....;
return d1.compareTo(d2);
}
}