I'm writing an app for android that needs to parse data from an XML file. I've never come across an error like this that is so impossibly hard to track down. Or maybe my brain just stopped working. That happens. XML file is of the form:
<?xml version="1.0" encoding="iso-8859-1"?>
<memberRoster>
<agent>
<agentInfo1>...</agentInfo1>
<agentInfo2>...</agentInfo2>
...
</agent>
<agent>
...
</agent>
...
</memberRoster>
So far it's working well, except for some random bits of fun!
Every now and then it will throw a NullPointerException. I did some more digging and found out that there are THREE "agents" (out of 800) with "supposedly" null data. I checked the XML file and the data is there, there are no illegal characters, etc. It is the same three "agents" every time. The program parses other entries before and after these "null" "agents". Also of note is that not all "agentInfo" fields in the ArrayList come up null; example, one of the entries has 7 of the 8 entries as null, with the 8th one non-null, another has only one null with the last 7 non-null.
I'm parsing the data in to an ArrayList from the XML file, and like I mentioned before, it works flawlessly until it comes to those three specific entries in the XML file.
I'm sorry I can't give much more info than that, the data is sensitive to our members.
EDIT:
Sorry! I knew I was forgetting something! :)
Some code from my XMLHandler.java class:
public void characters(char[] ch, int start, int length)
if(this.in_mr_agentNrdsId) {
agent[0] = ch.toString();
}
else if(this.in_mr_agentFirstName) {
agent[1] = ch.toString();
}
else if(this.in_mr_agentLastName) {
agent[2] = ch.toString();
}
else if(this.in_mr_agentPhone) {
agent[3] = ch.toString();
}
else if(this.in_mr_agentEmail) {
agent[4] = ch.toString();
}
else if(this.in_mr_agentOfficeName) {
agent[5] = ch.toString();
}
else if(this.in_mr_agentOfficePhone) {
agent[6] = ch.toString();
}
else if(this.in_mr_agentType) {
agent[7] = ch.toString();
pds.setMemberRoster(agent);
agent = new String[8];
}
PDS is an object of type ParsedDataSet, which is just a simple class containing the ArrayList objects and a few getter and setter methods:
public class ParsedDataSet {
private ArrayList agentOpenHouses = new ArrayList();
private ArrayList calendarOfEvents = new ArrayList();
private ArrayList latestStatistics = new ArrayList();
private ArrayList memberRoster = new ArrayList();
public ArrayList<String[]> getAgentOpenHouses() {
return agentOpenHouses;
}
public ArrayList<String[]> getCalendarOfEvents() {
return calendarOfEvents;
}
public ArrayList<String[]> getLatestStatistics() {
return latestStatistics;
}
public ArrayList<String[]> getMemberRoster() {
return memberRoster;
}
public void setAgentOpenHouses(String[] agentOpenHousesItem) {
this.agentOpenHouses.add(agentOpenHousesItem);
}
public void setCalendarOfEvents(String[] calendarOfEventsItem) {
this.calendarOfEvents.add(calendarOfEventsItem);
}
public void setLatestStatistics(String[] latestStatisticsItem) {
this.latestStatistics.add(latestStatisticsItem);
}
public void setMemberRoster(String[] memberRosterItem) {
this.memberRoster.add(memberRosterItem);
}
} // end class ParsedDataSet
You could throw an if statement into your assignements and reassign any caught 'NULL' or empty strings into a zero value or just reassign as variable = "" in your code.
For example:
if (agentInfo1 == NULL) {
agentInfo1 = "" || agentInfo1 = 0; //Depending on what your variables are
}
Try putting try catch loop in code to find where the error is happening, then, pinpoint the exact part of code that is giving this error, there do null checks before proceeding. This is based on best practices of software development, rather than a fix for you.
Alternatively, you can makes sure on server side that there are no "null" values, maybe by giving dummy value like "EMPTY_STRING". This is especially relevant if your app is already shipped and you cant make any client code changes.
Related
I searched for related questions but didn´t find a solution (at least i don´t know if i named it correctly)
So, i have two ArrayLists and i would like to randomize all of them to get a value:
public class ListBox {
public static ArrayList listOne(){
ArrayList<Lists> listOne = new ArrayList<>();
listOne.add(new Item("Text One"));
listOne.add(new Item("Text Two"));
return listOne;
}
public static ArrayList listTwo(){
ArrayList<Lists> listTwo = new ArrayList<>();
listTwo.add(new Item("Text Three"));
listTwo.add(new Item("Text Four"));
return listTwo;
}
}
in other activity:
public void buttonClick(View view){
ArrayList<Lists> algumasListas = ListBox.listOne();
...
}
This is where i shuffle it
public class ListMixer extends ListBox{
public ArrayList<Lists> listas = null;
public ListMixer(ArrayList<Lists> listas ) {
this.listas = listas;
}
protected String mixList(){
Double randomNumber = new Double(Math.random() * listas.size());
int randomNum = randomNumber.intValue();
Lista lista= listas.get(randomNum);
String listaString2 = String.valueOf(lista);
String message = ("This is your list: " + listas);
return message;
}
}
my desired output would be one of the four listItems.
Appreciate the help!
Merge arrays into single one of size N.
Choose a random number in range 0..N-1.
Choose an element by index.
The first bug I'm seeing in your code is that listOne() returns object listTwo when called, which doesn't exist. It probably shouldn't even compile, unless something funky is going on with global scope variables.
The following code should do what you want by merging the two lists into one and then returning a random object from them.
public Object randomFromList(List<Object> listOne, List<Object> listTwo){
List<Object> bigList = new ArrayList<Object>(listOne.size() + listTwo.size());
bigList.addAll(listOne);
bigList.addAll(listTwo);
return bigList.get(new Random().nextInt(bigList.size()));
}
For optimization, if you call this a lot, I would save the Random() object outside of the method to avoid instantiating it every time you make the call.
Been struggling with this all day. I feel like I am one annotation away from the right solution.
I am getting an JSON from an API, and parsing it using Gson inside Volley request into a object.
Then I want to store the object in DB, using ORMLite.
The problem is that my JSON has lists of other objects. So I have decided that ForeignCollection are required.
Here is simplified version of what I am getting as JSON:
{
"b": [
{"title"="abc","id="24sfs"},
{"title"="def", "id="532df"}
],
"c": [
{"description"="abc","id="34325"},
{"description"="def", "id="34321"}
],
"id"="ejsa"
}
Lets call this whole object class A. The objects inside "b", are B, inside "c", class C.
B and C are the similar. This leads to the following class definitions:
class A {
#DatabaseField(index = true, unique = true, id = true)
private String id;
#ForeignCollectionField(eager = true)
public Collection<B> bCollection;
public ArrayList<B> b;
#ForeignCollectionField(eager = true)
public Collection<C> cCollection;
public ArrayList<C> c;
}
class B {
#DatabaseField(foreign=true)
public A a;
#DatabaseField(id = true, index = true, unique = true)
public String id;
#DatabaseField
public String title;
}
The reason we need the ArrayList b and c, is so that gson can parse it correctly. So once I have class A in memory, here is what I do to store it
private void storeA(A a) {
if (a.b != null) {
getHelper().getDao(B.class).callBatchTasks(new Callable<Void>() {
#Override
public Void call() throws Exception {
for (B b : a.b) {
b.a = a;
try {
getHelper().getDao(B.class).createOrUpdate(b);
} catch (Exception e) {
}
}
return null;
}
});
}
/*
Here we start running into problems. I need to move the data from the ArrayList to the Collection
*/
a.bCollection = a.b; // but this seems to work, since bCollection is a Collection
a.cCollection = a.c;
getHelper().getDao(A.class).createOrUpdate(a);
}
So it seems to store correctly, no errors as far as I can tell. But when I try to retrieve as follows, I can't retrieve anything out of bCollection:
private void load() {
try {
List<A> as = getHelper().getDao(A.class).queryForEq("id", "ejsa");
if (as != null && as.size() > 0) {
A a = as.get(0);
CloseableWrappedIterable<B> cwi = a.bCollection.getWrappedIterable();
try {
for (B b : cwi) {
Log.e(b.title);
}
} finally {
cwi.close();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
What am I doing wrong? Do I need to specify foreignColumnName for some of these things? I can't tell if the things are not being stored correctly or if I am just failing to retrieve them correctly?
I would try removing the following two lines:
a.bCollection = a.b;
a.cCollection = a.c;
A's ForeignCollection's should be auto-magically populated for you by ORMLite when you query for A, you do not need to set them yourself.
This question already has answers here:
How to remove duplicates from a list?
(15 answers)
Closed 8 years ago.
I want to remove duplicates from ArrayList of type Alerts where Alerts is a class.
Class Alerts -
public class Alerts implements Parcelable {
String date = null;
String alertType = null;
String discription = null;
public Alerts() {
}
public Alerts(String date, String alertType, String discription) {
super();
this.date = date;
this.alertType = alertType;
this.discription = discription;
}
}
Here is how I added the elements -
ArrayList<Alerts> alert = new ArrayList<Alerts>();
Alerts obAlerts = new Alerts();
obAlerts = new Alerts();
obAlerts.date = Date1.toString();
obAlerts.alertType = "Alert Type 1";
obAlerts.discription = "Some Text";
alert.add(obAlerts);
obAlerts = new Alerts();
obAlerts.date = Date2.toString();
obAlerts.alertType = "Alert Type 1";
obAlerts.discription = "Some Text";
alert.add(obAlerts);
What I want to remove from them-
I want all alerts which have unique obAlerts.date and obAlerts.alertType. In other words, remove duplicate obAlerts.date and obAlerts.alertType alerts.
I tried this -
Alerts temp1, temp2;
String macTemp1, macTemp2, macDate1, macDate2;
for(int i=0;i<alert.size();i++)
{
temp1 = alert.get(i);
macTemp1=temp1.alertType.trim();
macDate1 = temp1.date.trim();
for(int j=i+1;j<alert.size();j++)
{
temp2 = alert.get(j);
macTemp2=temp2.alertType.trim();
macDate2 = temp2.date.trim();
if (macTemp2.equals(macTemp1) && macDate1.equals(macDate2))
{
alert.remove(temp2);
}
}
}
I also tried-
HashSet<Alerts> hs = new HashSet<Alerts>();
hs.addAll(obAlerts);
obAlerts.clear();
obAlerts.addAll(hs);
You need to specify yourself how the class decides equality by overriding a pair of methods:
public class Alert {
String date;
String alertType;
#Override
public boolean equals(Object o) {
if (this == 0) {
return true;
}
if ((o == null) || (!(o instanceof Alert)))
return false;
}
Alert alert = (Alert) o;
return this.date.equals(alert.date)
&& this.alertType.equals(alert.alertType);
}
#Override
public int hashCode() {
int dateHash;
int typeHash;
if (date == null) {
dateHash = super.hashCode();
} else {
dateHash = this.date.hashCode();
}
if (alertType == null) {
typeHash = super.hashCode();
} else {
typeHash = this.alertType.hashCode();
}
return dateHash + typeHash;
}
}
You can then loop through your ArrayList and add elements if they aren't already there as Collections.contains() makes use of these methods.
public List<Alert> getUniqueList(List<Alert> alertList) {
List<Alert> uniqueAlerts = new ArrayList<Alert>();
for (Alert alert : alertList) {
if (!uniqueAlerts.contains(alert)) {
uniqueAlerts.add(alert);
}
}
return uniqueAlerts;
}
However, after saying all that, you may want to revisit your design to use a Set or one of its family that doesn't allow duplicate elements. Depends on your project. Here's a comparison of Collections types
You could use a Set<>. By nature, Sets do no include duplicates. You just need to make sure that you have a proper hashCode() and equals() methods.
In your Alerts class, override the hashCode and equals methods to be dependent on the values of the fields you want to be primary keys. Afterwards, you can use a HashSet to store already seen instances while iterating over the ArrayList. When you find an instance which is not in the HashSet, add it to the HashSet, else remove it from the ArrayList. To make your life easier, you could switch to a HashSet altogether and be done with duplicates per se.
Beware that for overriding hashCode and equals, some constraints apply.
This thread has some helpful pointers on how to write good hashCode functions. An important lesson is that simply adding together all dependent fields' hashcodes is not sufficient because then swapping values between fields will lead to identical hashCodes which might not be desirable (compare swapping first name and last name). Instead, some sort of shifting-operation is usually done before adding the next atomic hash, eg. multiplying with a prime.
First store your datas in array then split at as one by one string,, till the length of that data execute arry and compare with acyual data by if condition and retun it,,
HashSet<String> hs = new HashSet<String>();
for(int i=0;i<alert.size();i++)
{
hs.add(alert.get(i).date + ","+ alert.get(i).alertType;
}
alert.clear();
String alertAll[] = null;
for (String s : hs) {
alertAll = s.split(",");
obAlerts = new Alerts();
obAlerts.date = alertAll[0];
obAlerts.alertType = alertAll[1];
alert.add(obAlerts);
}
I have an android application, where parsing a json block takes around 250ms. It contains an array, and I only really need the first 6-7 values available immediatly. And I really need to speed up getting to those pieces of the data.
I have a data structure that essentially looks like:
class Data {
List<Map> data = objectmapper_readvalue_data;
public HashMap getItem(int i) {
return data.get(i);
}
}
I was really hoping to do something like this with a JsonParser:
class Data {
List data = new List();
JsonParser p;
public HashMap getItem(int i) {
while (data.length < i) {
data.append(p.parseOneBlockOfData());
}
return data.get(i);
}
}
And only the first 5-6 values will be parsed at the first render, the others I can deal with later. However, I'm missing the "parseOneBlockOfData" function. Of course I can use a StringBuilder to buffer every value in the parse until I find the next entire block, then use a objectParser or that, but I'm not sure what the performance will be like.
Are there any non hackish ways of doing this?
incase anyone googles this:
JsonParser parser = objectMapper.getFactory().createJsonParser(inputStream);
// Keep going until we find filters:
String fieldName = null;
JsonToken token = null;
while (!"filters".equals(fieldName)) {
token = parser.nextToken();
while (token != JsonToken.START_ARRAY) {
token = parser.nextToken();
}
fieldName = parser.getCurrentName();
}
// We're at the filters node
while (parser.nextToken() == JsonToken.START_OBJECT) {
Map x = objectMapper.readValue(parser, Map.class);
}
I am getting the most bizzarre behavior with trying to parse an XML, I run through it step by step and all values are assigned and retrieved in order and then the object I create is added to a HashMap for easy look up, the problem is when I am done retrieving it all the HashMap has null values and the ones that aren't null are the value of the very last node that was read, I have walked through it over and over and it all seems correct, but when it's done loading the values in the HasMap look like:
[0] null
[1] NarrationItem#44e9d170
[2] null
[3] null
[4] NarrationItem#44e9d170
etc, etc.
The format of my XML files is:
<narrations>
<narration id="0" name="A" alias="a" >
<line text="This is a test."></line>
</narration>
<narration id="1" name="B" alias="b" >
<line text="This another a test."></line>
</narration>
<narration id="2" name="C" alias="c" >
<line text="This is STILL a test."></line>
</narration>
</narrations>
And my XML parsing method is follows:
public HashMap<String, NarrationItem> NarrationMap = new HashMap<String, NarrationItem>();
private void LoadNarrationsXML() {
NarrationItem i = new NarrationItem();
String line;
String s;
try {
// Get the Android-specific compiled XML parser.
XmlResourceParser xmlParser = this.getResources().getXml(R.xml.narrations);
while (xmlParser.getEventType() != XmlResourceParser.END_DOCUMENT) {
if (xmlParser.getEventType() == XmlResourceParser.START_TAG) {
s = xmlParser.getName();
if (s.equals("narration")) {
i.Clear();
i.ID = xmlParser.getAttributeIntValue(null, "id", 0);
i.Name = xmlParser.getAttributeValue(null, "name");
i.Alias = xmlParser.getAttributeValue(null, "alias");
} else if (s.equals("line")) {
line = xmlParser.getAttributeValue(null, "text");
i.Narration.add(line);
}
} else if (xmlParser.getEventType() == XmlResourceParser.END_TAG) {
s = xmlParser.getName();
if (s.equals("narration")) {
NarrationMap.put(i.Alias, i);
}
}
xmlParser.next();
}
xmlParser.close();
} catch (XmlPullParserException xppe) {
Log.e(TAG, "Failure of .getEventType or .next, probably bad file format");
xppe.toString();
} catch (IOException ioe) {
Log.e(TAG, "Unable to read resource file");
ioe.printStackTrace();
}
}
The NarrationItem object is a custom object defined as:
public class NarrationItem {
int ID;
String Name;
String Alias;
ArrayList<String> Narration = new ArrayList<String>();
public NarrationItem() { }
public void LoadNarration(int id, String name, String alias, ArrayList<String> narration) {
ID = id;
Name = name;
Alias = alias;
Narration.addAll(narration);// = narration;
}
public void Clear() {
ID = 0;
Name = "";
Alias = "";
Narration.clear();
}
}//End Narration
If someone could point out the problem I'd be very thankful I have sat here staring at this issue for hours.
You're only ever creating one NarrationItem object - you're then using a reference to that object as the value for multiple entries in the map. Don't do that. You need to understand that the map doesn't contain an object as the value - it contains a reference to an object.
You can probably fix this just by creating a new NarrationItem each time instead of calling Clear.
It's not clear how you're looking at the map to see those null values, but if you're using the debugger and looking at the internal data structure, you probably shouldn't really be doing that either - instead, step through the keys, values or entries, i.e. stick within the abstraction that HashMap is meant to support.