Develop Reference

(android) Can I use this code in my DiffUtill implementation?

I am now making a DiffUtil class to update only changed items in the RecyclerView.
I have seen several other sample code.
When comparing two objects, they compared unique values ​​such as id defined in the Model(Data) class in areItemsTheSame().
However, I think it is difficult to assign an id or unique value to the List, or the code is messy.
Do I have to define and compare id like this?
Do I really need to define a unique Id variable in the Model class that separates each object?
Or shouldn't I use simply the equals()?
Using this Is it not just comparing the address of the object, but also the contents of the object?
As an additional question
What is the difference between DiffUtil.CallBack and DiffUtil.ItemCallBack?
This is my code.
RoutineModel.java
public class RoutineModel {
private ArrayList<RoutineDetailModel> routineDetailModels;
private String routine;
public RoutineModel(ArrayList<RoutineDetailModel> items, String routine) {
this.routine = routine;
this.routineDetailModels = items;
}
public ArrayList<RoutineDetailModel> getDetailItemList() {
return routineDetailModels;
}
public int getDetailItemSize() {
return routineDetailModels.size();
}
public String getRoutine() {
return routine;
}
public void setRoutine(String routine) {
this.routine = routine;
}
}
RoutineDiffUtil.java
public class RoutineDiffUtil extends DiffUtil.Callback {
private final List<RoutineModel> oldRoutineList;
private final List<RoutineModel> newRoutineList;
public RoutineDiffUtil(ArrayList<RoutineModel> oldRoutineList, ArrayList<RoutineModel> newRoutineList) {
this.oldRoutineList = oldRoutineList;
this.newRoutineList = newRoutineList;
}
#Override
public int getOldListSize() {
return oldRoutineList.size();
}
#Override
public int getNewListSize() {
return newRoutineList.size();
}
#Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return oldRoutineList.equals(newRoutineList);
}
#Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
return oldRoutineList.equals(newRoutineList);
}
}

You got wrong the meaning of areItemsTheSame() and areContentsTheSame() callbacks. As you see, there are oldItemPosition and newItemPosition arguments in them. You should use them to compare specific items – not lists themselves.
In areItemsTheSame() you have to check whether model at "old" position in the old list equals a model at "new" position in the new list. This is how DiffUtil knows if it has to make reordering animations.
areContentsTheSame() will be called for two items if and only if you return true for them in the previous callback. Here you have to check whether visual representation of "old" and "new" models is the same. This is how DiffUtil knows if it has to make "item changing" animations.
To compare two models you have to override equals() and hashCode(). There you specify conditions under which you consider two models the same. For example, if they have same routine. I don't the know context of your task so I can't tell you exactly how to implement them, but usually you just compare all fields. Probably adding an id field is a good idea too. Then you can consider models "equal" if they have same id. And in hashCode() you can just return Objects.hash(id).
Now, speaking about your question about ItemCallback. Formally, here is the explanation from docs:
DiffUtil.Callback serves two roles - list indexing, and item diffing. ItemCallback handles just the second of these, which allows separation of code that indexes into an array or List from the presentation-layer and content specific diffing code.
Practically, ItemCallback just has less methods to implement and is used together with AsyncListDiffer. It's just because missing methods are already implemented under the hood in AsyncListDiffer.

You have to override the equals and hashcodes of your model classes.
RoutineModel:
class RoutineModel {
private ArrayList<RoutineDetailModel> routineDetailModels;
private String routine;
public RoutineModel(ArrayList<RoutineDetailModel> items, String routine) {
this.routine = routine;
this.routineDetailModels = items;
}
public ArrayList<RoutineDetailModel> getDetailItemList() {
return routineDetailModels;
}
public int getDetailItemSize() {
return routineDetailModels.size();
}
public String getRoutine() {
return routine;
}
public void setRoutine(String routine) {
this.routine = routine;
}
#Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
RoutineModel that = (RoutineModel) o;
return Objects.equals(routineDetailModels, that.routineDetailModels) &&
Objects.equals(routine, that.routine);
}
#Override
public int hashCode() {
return Objects.hash(routineDetailModels, routine);
}
}
RoutineDiffUtil:
public class RoutineDiffUtil extends DiffUtil.Callback {
private final List<RoutineModel> oldRoutineList;
private final List<RoutineModel> newRoutineList;
public RoutineDiffUtil(ArrayList<RoutineModel> oldRoutineList, ArrayList<RoutineModel> newRoutineList) {
this.oldRoutineList = oldRoutineList;
this.newRoutineList = newRoutineList;
}
#Override
public int getOldListSize() {
return oldRoutineList.size();
}
#Override
public int getNewListSize() {
return newRoutineList.size();
}
#Override
public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
return oldRoutineList.get(oldItemPosition).getRoutine().equals(newRoutineList.get(newItemPosition).getRoutine());
}
#Override
public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
return oldRoutineList.get(oldItemPosition).equals(newRoutineList.get(newItemPosition));
}
}
And don't forget to override the equals and hashcode of your RoutineDetailModel.

How to define drools rule for list of string as POST method in POSTMAN

public class QuestionnaireReq {
private String questionId;
private List<String> answerText;
public String getQuestionId() {
return questionId;
}
public void setQuestionId(String questionId) {
this.questionId = questionId;
}
public List<String> getAnswerText() {
return answerText;
}
public void setAnswerText(List<String> answerText) {
this.answerText = answerText;
}
}
and drools file
rule "qustionRule_3"
when
questionnaireReq : QuestionnaireReq(questionId=="q2" && $answerText=="Web UI front-end");
questionnaireRes : QuestionnaireRes();
then
questionnaireRes.setNextQuestionId("q3");
end
and postman request here
{
"questionId":"q3",
"answerText":["Web UI front-end","Web Back-end"]
}

I think what you're trying to ask is how to update your rule to check that a value is in a list, since your original rule is trying to do an == which will never match since you're comparing a list to a string.
In this case you'll want to use the Drools contains operator, which verifies that a list contains a given element.
rule "qustionRule_3"
when
questionnaireReq : QuestionnaireReq( questionId=="q2",
answerText contains "Web UI front-end")
questionnaireRes : QuestionnaireRes()
then
questionnaireRes.setNextQuestionId("q3");
end
You can read more about the contains operator in the official Drools documentation, in the section called "Supported operators in DRL pattern constraints".

compare two objects of same class which contain list of objects

I have two objects(which contain of list of objects) of same class.I need to find whether both are same or not.
Consider below example:
class Device {
String deviceName;
String devLocation;
String devType;
String devID;
public String getDeviceName() {
return deviceName;
}
public void setDeviceName(String deviceName) {
this.deviceName = deviceName;
}
public String getDevLocation() {
return devLocation;
}
public void setDevLocation(String devLocation) {
this.devLocation = devLocation;
}
public String getDevType() {
return devType;
}
public void setDevType(String devType) {
this.devType = devType;
}
public String getDevId() {
return devID;
}
public void setDevId(String devId) {
this.devID = devId;
}
}
class DevList {
List<Device> deviceList;
public List<Device> getDevices() {
return deviceList;
}
public void setDevices(List<Device> deviceList) {
this.deviceList = deviceList;
}
}
Need to compare two objects of DevList class.
Will get a new DevList object for every regular interval of time.
Every time i need to verify current object with previous object and update DB if there is any difference else ignore.
The list(deviceList) in current and previous objects might not be in same order.
for example:
Consider below two objects which are in Json format(Please ignore json format errors).
Object 1:
{
"devList":[
{
"deviceName":"ABC",
"devLocation":"India",
"devType":"Router",
"devID":"1111"
},
{
"deviceName":"XYZ",
"devLocation":"India",
"devType":"Router",
"devID":"2222"
}
]
}
Object 2:
{
"devList":[
{
"deviceName":"XYZ",
"devLocation":"India",
"devType":"Router",
"devID":"2222"
},
{
"deviceName":"ABC",
"devLocation":"India",
"devType":"Router",
"devID":"1111"
}
]
}
We can do it by iterating lists in both objects by checking devID. But complexity would be M*N.
Is there any other way?

You could override equals in Device to compare each Device object.
Something similar
class Device {
...
...
//your getter and setter
public boolean equals (Object obj)
{
if (Device.class != obj.getClass()) {
return false;
}
if (obj instanceof Device) {
return (deviceName.equals(((Device) obj).deviceName) &&
devLocation.equals(((Device) obj).devLocation) &&
devType.equals(((Device) obj).devType) &&
devID.equals(((Device) obj).devID));
}
return false;
}
}
Now, call removeAll, which will remove same object list from List1
List1.equals(List2);
So, if both list has same object list, then List1 would be empty.

Step 1: First override equal method in Device Class
Step 2: override the equal() in your DevList class with
with below logic
1. use one Set collection
2. add object into it from 1st Object's list
3. check size() of set
3. add object from 2nd Object's list
5. check size() of set every time you add from 2nd list
6. if more than the size of one list it is not equal(As Set will not keep duplicate value)

How to create object based on boolean condition?

I have an Item object having 4 String fields and 3 boolean fields.
I have to construct this object based on the 3 boolean variables.
The target is whenever any one of the boolean variable is true we have to create the object having that/those boolean variable set.
If for any situation none of the boolean variables are true, we wont create the object.
I am using a COR to check whether any of the boolean fields will be set or not based on some business logic.
I was trying this with builder, but then I have to construct so many objects and later discard them when none of the boolean variables found true.
Can anyone have any better idea, to solve this kind of problem ?
Well thanks for the 2 delete flag for this question. Thank for the thoughts on this question as well.
I did something to achieve what I want. Which is quite flexible I believe. Only part if there is a dependency on If loop, but that is acceptable since Report class can have extra boolean so when that class is changed, it's builder should be touched to cater that change. Rest this is flexible which I wanted.
public class Report {
private String acftNo;
private Date plannedDate;
private String plannedStn;
private Integer mntncId;
private Set<String> capableStations;
private String routedStn;
private boolean isRoutedNEQPlannedStn; //Inconsistency type 1
private boolean isCapableAtPlannedStn; //Inconsistency type 2
private boolean isPlannedOrRoutedStationExists; //Inconsistency type 3/5
public Report(String acftNo, Integer mntncId) {
super();
this.acftNo = acftNo;
this.mntncId = mntncId;
}
public Report(String acftNo, Date plannedDate, String plannedStn,
Integer mntncId) {
super();
this.acftNo = acftNo;
this.plannedDate = plannedDate;
this.plannedStn = plannedStn;
this.mntncId = mntncId;
}
//setters and getters. Removed for space.
public static Report buildReport(Maintenance<?> task, Set<InconsistencyReport> enumSet) {
Report temp = new Report(task.getAssignment().getAircraftNumber(),task.getAssignment().getMntncScheduleDate(),
task.getAssignment().getStationCode(),task.getAssignment().getMntncId());
temp.setCapableStations(InconsistencyReport.getCapableStations(task));
for(InconsistencyReport ir : enumSet)
{
if(ir.compareTo(InconsistencyReport.ROUTED_STN_NEQ_PLANNED_STN)==0)
temp.setRoutedNEQPlannedStn(true);
if(ir.compareTo(InconsistencyReport.ITEM_NT_CAPABLE_AT_PLANNED_STN)==0)
temp.setCapableAtPlannedStn(true);
if(ir.compareTo(InconsistencyReport.NO_ROUTD_STN_ON_A_DATE)==0)
temp.setPlannedOrRoutedStationExists(true);
}
return temp;
}
}
calculateInconsitencyReport() method which will decide whether to create object or not.
public class InconsistencyReportChain {
public enum InconsistencyReport implements InconsistencyReportIface {
ROUTED_STN_NEQ_PLANNED_STN {
#Override
public boolean findInconsistency(Maintenance<?> task ) {
if(!validate(task))
return false;
//some logic
return true;
return false;
}
},
ITEM_NT_CAPABLE_AT_PLANNED_STN {
#Override
public boolean findInconsistency(Maintenance<?> task) {
if(!validate(task))
return false;
//some logic
return true;
return false;
}
},
NO_ROUTD_STN_ON_A_DATE {
#Override
public boolean findInconsistency(Maintenance<?> task) {
if(!validate(task))
return false;
//some logic
return true
return false;
}
};
#Override
public boolean validate(Maintenance<?> task) {
return !(null == task.getAssignment());
}
static Set<String> getCapableStations(Maintenance<?> task)
{
Set<String> capableStations = newHashSet();
if(task.getCapStationList() != null)
{
capableStations.addAll(Arrays.asList(task.getCapStationList().split(StringConstants.COMMA_SPLIT_REGEX)));
}
if(task.getCapStationClassList() != null)
{
Map<String, List<String>> stationClassMap = CacheManager.get(STN_CLASS.name());
List<String> stationClass = Arrays.asList(task.getCapStationClassList().split(StringConstants.COMMA_SPLIT_REGEX));
for(String stnClass : stationClass)
{
capableStations.addAll(stationClassMap.get(stnClass));
}
}
return capableStations;
}
}
public static Report calculateInconsitencyReport(Maintenance<?> task) {
Set<InconsistencyReport> enumSet = null;
for(InconsistencyReport iReport : InconsistencyReport.values())
{
if(iReport.findInconsistency(task))
{
if(null==enumSet)
enumSet = EnumSet.of(iReport);
else
enumSet.add(iReport);
}
}
if(null!= enumSet && enumSet.size() > 0)
return Report.buildReport(task,enumSet);
return null;
}
}
Helper Interface:
public interface InconsistencyReportIface {
public boolean findInconsistency(Maintenance<?> task );
public boolean validate(Maintenance<?> task );
}
Details of class logic is teared off because of security.

What is the problem? Just create your object when one of your booleans is true.
if(bool1 || bool2 || bool3) {
item = new Item(str1, str2, str3, str4, bool1, bool2, bool3);
}

From what I understand of your description:
a) you will have some bools that will determine wether you create a certain object or not.
b) you may have to include some more bools into the "check protocol"
c) you have to do this checking in a loop where
i/ you check for the bool variable
ii/ you check if the object had been created previously
I still don't quite get it yet, but.. that looks pretty straight forward to me. Let's say your bools are stored in a boolean array boolean[] bools and your strings in a string array String[] strings (which, btw, I don't know what they are used for). You are saying to check if every bool is true and then create an object based on that result.
boolean[] bools = new boolean[] { ... };
String[] strings = new String[] { ... };
boolean checks = false;
for(int i = 0; i<bools.length && !checks; i++)
checks = bools[i];
//so far we will have processed if any of the bools was false, which was your condition
if(checks)
Object object = new Object(); //create your desired object
I don't understand why you would need to check if the object has been constructed previously, though, so I didn't include it in my suggestion :P

checking whether an object is present in a List of Objects on the basis of some member variable

suppose I have defined a List as
private BlockingQueue<MyDelayed> DelayedIds = new DelayQueue<>();
class MyDelayed is like:
private class MyDelayed implements Delayed {
private String myId;
private Long creationTime;
MyDelayed (String myId) {
this.myId= myId;
this.creationTime = System.currentTimeMillis();
}
String getMyId() {
return this.myId;
}
#Override
public long getDelay(TimeUnit unit) {
//TODO
}
#Override
public int compareTo(Delayed o) {
//TODO
}
}
Now suppose that I want to add an Object of class MyDelayed in DelayedIds list.
I can do it by using add function.
But If I want to add obbject in list only if list does not contain an object of class MyDelayed which has the same myId attribute which I am trying to insert.
Obviously DelayedIds .contains(new MyDelayed(myId)) will not work.
Is there any easy way to check this thing ?
Am I missing something ?

You could write something like this and compare every element in the list to see if it contains your id. If at any point you find a matching one you return true, if the loop finished having found none it returns false.
public boolean contains(String id){
for (MyDelayed md : DelayedIds){
if(md.getMyId().equals(id)){
return true;
}
}
return false;
}
Now to check before adding you would do something like:
if(!contains(myNewObject.getMyId())){
DelayedIds.add(myNewObject)
}
Also, I'd suggest that you rename DelayedIds to delayedIds in order to follow coding standards (see Variables).