could somebody help me to solve my code problem? Error is:
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)
at java.util.HashMap$KeyIterator.next(HashMap.java:928)
at javaTest.Main.main(Main.java:18)
Code is:
public static void main(String arg[]) {
job.add("a");
job.add("b");
HashSet<String> klonasOnJob = job;
for (String p : klonasOnJob) {
if (p != "b") {
} else {
job.remove(p);
}
}
Most collections will break and throw ConcurrentModificationException if you modify the collection (in your case by removing an element) while iterating over the collection. Use the iterator's remove() method instead.
In your case the relevant fragment would be:
Iterator<String> it = klonasOnJob.iterator();
while (it.hasNext()) {
String p = it.next();
if (p != "b") {
} else {
it.remove();
}
}
Related
While saving Map type data in couchBase I am getting an exception
Caused by: org.springframework.data.mapping.MappingException: Couldn't find PersistentEntity for type java.lang.Object!
I've taken a map in DataModel
#Data
public class test {
private Map<String,Object> testMap;
}
I found this and override couchBase configuration to do customMapping in case of Object Type like
protected <R> R read(final TypeInformation<R> type, final CouchbaseDocument source,
final Object parent) {
if (Object.class == typeMapper.readType(source, type).getType()) {
return (R) source.export();
} else {
return super.read(type, source, parent);
}
}
It worked for the request like
{
"dummyMap":{
"key1":"val1",
"key2":"val2"
}
}
But failed for
{
"dummyMap":{
"key1":"val1",
"key2":"val2",
"objects":[
{
"key1":"val1",
"key2":"val2"
}
]
}
}
with exception
Caused by: java.lang.IllegalArgumentException: Basic type must not be null!
I guess it is because of the array. Please let me know what I am doing wrong.
I am using spring-data-couchbase version 2.0.4.RELEASE.
hi please use below code, its because type is null and couchbase mapping convertor cant read document
its must be work.
#Override
#SuppressWarnings("unchecked")
protected <R> R read(final TypeInformation<R> type, final CouchbaseDocument source, final Object parent) {
if (type == null)
return (R) source.export();
if (Object.class == typeMapper.readType(source, type).getType()) {
return (R) source.export();
} else {
return super.read(type, source, parent);
}
}
I'm trying to implement my own custom exceptions in dot net core.
This is what I have so far:
public class WSException: Exception
{
// some custom stuff...
private readonly string _developerMessage = "";
public string DeveloperMessage { get { return _developerMessage; } }
public WSException() {}
public WSException(string message) : base(message) {
this._developerMessage = message;
}
public WSException(string message, Exception inner) : base(message, inner) {
this._developerMessage = message;
}
public WSException(Exception ex) : base(ex.Message, ex.InnerException) {
_developerMessage = ex.Message;
Source = ex.Source;
//StackTrace = ex.StackTrace; // cannot be assigned to, it's read only
}
public WSException(string message) : base(message) {
this._developerMessage = (String.IsNullOrWhiteSpace(developerMessage) ? message : developerMessage);
}
}
When I catch a general exception, I try to create one of my own (a WSException) to handle it in a common way, like this:
try {
// whatever
}
catch (WSException e) {
HandleException(e);
}
catch (Exception e) {
HandleException(new WSException(e));
}
When I do it like that, e.Source and e.StackTrace are null, and when I try to assign StackTrace I get a Propery or indexer 'Exception.StackTrace' cannot be assigned to --it is read only.
How should such I implement this constructor?
public WSException(Exception ex) : base(ex.Message, ex.InnerException) {
_developerMessage = ex.Message;
Source = ex.Source;
//StackTrace = ex.StackTrace; // cannot be assigned to, it's read only
}
The workaround I found so far is to handle it when I'm serializing the error to json, something like this:
public class WSExceptionJsonConverter : JsonConverter
{
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
var ex = value as WSException;
writer.WriteStartObject();
// buch of properties[...]
string stackTrace = null;
if (ex.StackTrace != null) {
stackTrace = ex.StackTrace;
} else if (ex.InnerException != null && ex.InnerException.StackTrace != null) {
stackTrace = ex.InnerException.StackTrace;
} else {
stackTrace = null;
}
writer.WritePropertyName("stacktrace");
serializer.Serialize(writer, stackTrace.Split('\n'));
writer.WriteEndObject();
}
But it feels too hacky
I've written an CustomResourceHandler to add a version number to my js and css files, which works fine, but all primefaces resources get a double version number now.
Without CustomResourceHandler:
javax.faces.resource/jquery/jquery-plugins.js.xhtml?ln=primefaces&v=6.0.17
With CustomResourceHandler:
javax.faces.resource/jquery/jquery-plugins.js.xhtml?ln=primefaces&v=6.0.17&v=6.0.17
My CustomResourceHandler:
public class ExtendedResourceHandler extends PrimeResourceHandler {
public ExtendedResourceHandler(ResourceHandler wrapped) {
super(wrapped);
}
#Override
public Resource createResource(String resourceName, String libraryName) {
if (!org.primefaces.util.Constants.LIBRARY.equalsIgnoreCase(libraryName)
&& !org.primefaces.extensions.util.Constants.LIBRARY.equalsIgnoreCase(libraryName) && !"javax.faces".equalsIgnoreCase(libraryName) && resourceName != null
&& (resourceName.endsWith(".css") || resourceName.endsWith(".js"))) {
final Resource resource = super.createResource(resourceName, libraryName);
if (resource == null) {
return null;
}
return new ResourceWrapper() {
#Override
public String getRequestPath() {
String resultPath = super.getRequestPath();
resultPath += (resultPath.contains("?") ? "&" : "?") + "version=V6326";
return resultPath;
}
#Override
public Resource getWrapped() {
return resource;
}
};
} else {
return super.createResource(resourceName, libraryName);
}
}
}
faces-config.xml:
<resource-handler>de.sync4.cockpit.web.beans.resourcehandler.ExtendedResourceHandler</resource-handler>
Because of that problem I can't get the pe:ckEditor to work, because it can't find necessary resources. Any idea what's wrong with my Handler?
Found the Problem. I needed to extend the ResourceHandlerWrapper, not the PrimeResourceHandler.
I also have an ExtendedBeanELResolver. I had to return null there if the base object is an instance of my custom handler.
This is my first post here. I am trying to create a singly link list. I am using AtEnd and AtStart methods to insert values at the end or in the beginning of the list and using display method to print all the values. The insertion methods seems to be working fine (at least I think so) but whenever I call display method it shows only the first value and then there is a null pointer exception. For example when I run this code I see only 9 and then there is the NPE despite the fact that I have put a check on the display method for "not null".
class node {
private int data;
private node next;
node() {
}
node(int data) {
this.data = data;
this.next = null;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data=data;
}
public node getNext() {
return next;
}
public void setNext(node next) {
this.next = next;
}
}
public class list extends node {
node head;
list() {
}
public void AtStart(int val) {
node n = new node(val);
if (head == null) {
head=n;
} else {
n.setNext(head);
int temp = head.getData();
head.setData(val);
n.setData(temp);
//n = head;
}
}
public void AtEnd(int val) {
if (head == null) {
node n = new node(val);
head = n;
} else {
node t = head;
for(; t.getNext() != null; ) {
if(t.getNext() == null) {
t.setNext(new node (val));
}
t = t.getNext();
}
}
}
public void display() {
node t = head;
for(; t.getNext() == null;) {
if (t !=null) {
System.out.println(t.getData());
t = t.getNext();
}
}
}
}
public static void main(String args[]) {
list l = new list();
l.AtStart(16);
l.AtEnd(6);
l.AtEnd(36);
l.AtStart(9);
l.AtEnd(22);
l.display();
}
i dont get what your AtStart function does, it should be much simpler:
public void AtStart(int val){
if(head==null){
head=n;
}
else{
head.setnext(head);
head.setData(val);
}
}
Every programmer ends up with a set of utility classes after a while. Some of them are true programming pearls and they are reused in several of your projects. For example, in java:
class Separator {
private String separator;
private boolean called;
public Separator(String aSeparator) {
separator = aSeparator;
called = false;
}
#Override
public String toString() {
if (!called) {
called = true;
return "";
} else {
return separator;
}
}
}
and:
public class JoinHelper {
public static <T> String join(T... elements) {
return joinArray(" ", elements);
}
public static <T> String join(String separator, T... elements) {
return joinArray(separator, elements);
}
private static <T> String joinArray(String sep, T[] elements) {
StringBuilder stringBuilder = new StringBuilder();
Separator separator = new Separator(sep);
for (T element : elements) {
stringBuilder.append(separator).append(element);
}
return stringBuilder.toString();
}
}
What is your most reused class?
System.Object - almost all my types extend it.
A utility class that has logging and email functionality. An extensions class that contains extension methods. A reporting class that basically harness the reporting services web service and makes it easy to stream reports as excel, pdf, etc.
Examples...
1.) Utility Class (static)
public static void LogError(Exception ex)
{
EventLog log = new EventLog();
if (ex != null)
{
log.Source = ConfigurationManager.AppSettings["EventLog"].ToString();
StringBuilder sErrorMessage = new StringBuilder();
if (HttpContext.Current.Request != null && HttpContext.Current.Request.Url != null)
{
sErrorMessage.Append(HttpContext.Current.Request.Url.ToString() + System.Environment.NewLine);
}
sErrorMessage.Append(ex.ToString());
log.WriteEntry(sErrorMessage.ToString(), EventLogEntryType.Error);
}
}
2.) Extensions Class
public static IEnumerable<TSource> WhereIf<TSource>(this IEnumerable<TSource> source, bool condition, Func<TSource, bool> predicate)
{
if (condition)
return source.Where(predicate);
else
return source;
}
public static short getLastDayOfMonth(short givenMonth, short givenYear)
{
short lastDay = 31;
switch (givenMonth)
{
case 4:
case 6:
case 9:
case 11:
lastDay = 30;
break;
case 2:
if ((int)givenYear % 4 == 0)
{
lastDay = 29;
}
else
{
lastDay = 28;
}
break;
}
return lastDay;
}
Most reused but boring:
public static void handleException(Exception e) throws RuntimeException {
if (e instanceof RuntimeException) {
throw (RuntimeException) e;
}
throw new RuntimeException(e); //NOPMD
}
Less boring (also methods for building lists and sets):
/**
* Builds a Map that is based on the Bean List.
*
* #param items Bean List items
* #param keyField Bean Field that will be key of Map elements (not null)
* #return a Map that is based on the Bean List
*/
#SuppressWarnings("unchecked")
public static <T, K> Map<K, T> buildMapFromCollection(final Collection<T> items,
boolean linkedMap,
final String keyField,
final Class<K> keyType) {
if (items == null) {
return Collections.emptyMap();
}
if (keyField == null) {
throw new IllegalArgumentException("KeyField is null");
}
final Map<K, T> result;
if (linkedMap) {
result = new LinkedHashMap<K, T>();
} else {
result = new HashMap<K, T>();
}
BeanMapper mapper = null;
for (final T item : items) {
if (mapper == null) {
mapper = new BeanMapper(item.getClass());
}
final K key = (K) mapper.getFieldValue(item, keyField);
result.put(key, item);
}
return result;
}
Logger class: Which logs the flow of control in a log file.
Configuration Reader/Setter: which reads the configuration from ini/xml file and sets the environment of the application
Most reused? Hmmm...
boost::shared_ptr<> with boost::weak_ptr<>
probably most reused (also probably most bang-for-buck ratio)
Globals
Just a simple class with static DBConnString, and a few other app wide settings.
Have reused the simple file in about 2 dozen projects since working with .Net
A ConcurrentDictionary I wrote, which I now seem to use everywhere (I write lots of parallel programs)