Develop Reference

Compare Two JSON object

I am having JSON object like
{
key1:value1,
key2:value2
key3:value3
}
and i will write this JSON content to file.(Done)
For next interval of time i am getting JSON Object as
{
key1:newValue1,
key2:value2
key3:newValue3
}
I need to find out difference between each values. and need to write new json into file
{
key1:(value1- newValue1),
key2:(value2 - value2)
key3:(value3- newValue3)
}
How can i achieve it.? Please help.

The code below just iterates through the keys of your testObject, subtracts the value of the object from file and puts the result of this subtraction back to the testObject... Than you can save, or do whatever you want to do with the values in testObject
for(Iterator<String> iterator = testObject.keys(); iterator.hasNext();) {
String key = iterator.next();
try {
int testValue = testObject.getInt(key);
int fileValue = fileObject.getInt(key);
int differenceValue = testValue - fileValue;
testObject.put(key, differenceValue);
} catch (JSONException e) {e.printStackTrace();}
}

How to remove duplicates from ArrayList of type Object? [duplicate]

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);
}

Simple Android XML Parsing Task

I need to parse the following XML structure in my Android activity. I have it in String format:
<Cube>
<Cube time="2012-09-20">
<Cube currency='USD' rate='1.2954'/>
<Cube currency='JPY' rate='101.21'/>
<!-- More cube tags here -->
</Cube>
</Cube>
Out of this I want to get an array of currency names (USD, JPY, etc) and their respective rates. Optionally, the date which appears only once in the XML document in the format specified above. Note the empty Cube tag also. There might be other weird occurrences like this as well. I only need to get Cube tags that have both currency and rate set.
Preferably using some XML parsing library and not regex, but if it resorts to that I am ready to use it as well.
Edit:
Here's what I've come up with so far. The problem is with inserting the matched elements inside an array, which I don't know how to do.
Pattern p = Pattern.compile("<Cube\\scurrency='(.*)'\\srate='(.*)'/>");
Matcher matcher = p.matcher(currency_source);
while (matcher.find()) {
Log.d("mine", matcher.group(1));
}

Here is a custom handler that should get the data you want:
public class MyHandler extends DefaultHandler {
private String time;
// I would use a simple data holder object which holds a pair
// name-value(or a HashMap)
private ArrayList<String> currencyName = new ArrayList<String>();
private ArrayList<String> currencyValue = new ArrayList<String>();
#Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
if (localName.equals("Cube")) { // it's a Cube!!!
// get the time
if (attributes.getIndex("", "time") != -1) {
// this Cube has the time!!!
time = attributes.getValue(attributes.getIndex("", "time"));
} else if (attributes.getIndex("", "currency") != -1
&& attributes.getIndex("", "rate") != -1) {
// this Cube has both the desired values so get them!!!
// but first see if both values are set
String name = attributes.getValue(attributes.getIndex("",
"currency"));
String value = attributes.getValue(attributes.getIndex("",
"rate"));
if (name != null && value != null) {
currencyName.add(name);
currencyName.add(value);
}
} else {
// this Cube doesn't have the time or both the desired values.
}
}
}
}
Then you could use it along http://developer.android.com/reference/android/util/Xml.html or one of the thousands tutorials out there to parse your xml String.

Loading Content Values from JSON

I'm trying to load Content Values into a database. The code here works:
private void processTable(final JsonReader tableReader, final ModelLoader loader) throws IOException
{
tableReader.beginArray();
while (tableReader.hasNext()) {
String id = loader.getIdColumnName();
final ContentValues cv = loader.parseModel(tableReader);
persistData(loader.getTableName(),id, cv);
}
tableReader.endArray();
}
However, when I add an additional part into it, it fails.
private void processTable(final JsonReader tableReader, final ModelLoader loader) throws IOException
{
tableReader.beginArray();
while (tableReader.hasNext()) {
String id = loader.getIdColumnName();
final ContentValues cv = loader.parseModel(tableReader);
if (loader.getModelType() == Filter.LOADER.getModelType()) //Checks to see if the filter sub arrays are there
{
while(tableReader.hasNext())
{
String name = "";
try{
tableReader.
name = tableReader.nextName();
} catch (Exception e) {
tableReader.skipValue();
continue;
}
if (name.equals("ImageOverlays"))
processTable(tableReader, mLoader.getSpecificLoader("ImageOverlays"));
else if (name.equals("ColorOverlays"))
processTable(tableReader, mLoader.getSpecificLoader("ColorOverlays"));
}
}
persistData(loader.getTableName(),id, cv);
}
tableReader.endArray();
}
The purpose of the additional code is to get a particular item from the Filters and then process them. When I use this code, I don't even get any values for the Filters which I used to before.
I think that me skipping the values is somehow screwing up the ContentValues cv that I declare before it.
Thanks for any help.

So Its your Interior loop causing the problem which is skipping the JSON Objects that have to be parsed...
And Yeah the Content Values as you mentioned in the comments are not valid by the time you reach the end of the loop.

Android, Null Pointer Exception to Data that isn't null

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.