Java object already exists

java.lang.Object
java.lang.Throwable
java.lang.Exception
java.lang.RuntimeException
oracle.wcps.property.AlreadyExistsException

All Implemented Interfaces: java.io.Serializable

public class AlreadyExistsException

The AlreadyExistsException is thrown from a property service to indicate that the property entity being created already exists in the system.

Constructor Summary
AlreadyExistsException(java.lang.Class modelClass, IName name) Constructs an AlreadyExistsException indicating that the object of the specified class with the specified Name already exists in the system.
AlreadyExistsException(java.lang.Class modelClass, java.lang.String name) Constructs an AlreadyExistsException indicating that the object of the specified class with the specified name already exists in the system.
AlreadyExistsException(INamespaceName namespaceName) Constructs an AlreadyExistsException indicating that the specified Namespace already exists in the system.
AlreadyExistsException(IProperty property) Constructs an AlreadyExistsException indicating that the specified Property already exists in the system.
AlreadyExistsException(IPropertyDefinition definition) Constructs an AlreadyExistsException indicating that the specified PropertyDefinition already exists in the system.
AlreadyExistsException(IPropertySet propertySet) Constructs an AlreadyExistsException indicating that the specified PropertySet already exists in the system.
AlreadyExistsException(IPropertySetDefinition setDefinition) Constructs an AlreadyExistsException indicating that the specified PropertySetDefinition already exists in the system.

Methods inherited from class java.lang.Throwable
fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the specified Namespace already exists in the system. Parameters: namespaceName — — the Namespace pertaining to this exception.

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the specified PropertyDefinition already exists in the system. Parameters: definition — — the PropertyDefinition pertaining to this exception.

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the specified PropertySetDefinition already exists in the system. Parameters: setDefinition — — the PropertySetDefinition pertaining to this exception.

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the specified PropertySet already exists in the system. Parameters: propertySet — — the PropertySet pertaining to this exception.

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the specified Property already exists in the system. Parameters: property — — the Property pertaining to this exception.

AlreadyExistsException

Constructs an AlreadyExistsException indicating that the object of the specified class with the specified Name already exists in the system. Parameters: modelClass — — the object class pertaining to this exception. name — — the Name of the object pertaining to this exception.

AlreadyExistsException

public AlreadyExistsException(java.lang.Class modelClass, java.lang.String name)

Constructs an AlreadyExistsException indicating that the object of the specified class with the specified name already exists in the system. Parameters: modelClass — — the object class pertaining to this exception. name — — the name of the object pertaining to this exception.

Источник

Check if an object already exists in Java ArrayList

Then call queue.contains() to check if the queue contains the object.

Queue.queue.contains(p) // Call the contains method with the p object.

contains() will loop through the queue and check if the objects are equal to your p object by calling .equals() .

KvnH

Student of Software Development @ QUB

Comments

I want to check whether a patient object already exists in an ArrayList queue using the unique ID nhsNumber. But when I add a patient to the queue who I know already exists in the queue, the following code does not detect it. Any idea why this is?

public boolean checkIfInQueue(Patient p) < // set nhsNumber equal to the nhsNumberLabel on the page String nhsNumber = nhsNumberLabel.getText(); System.out.println("Checking if " + nhsNumber + " already in the queue"); // create boolean to state whether a person is in the queue or not (defaults to false) boolean isInQueue = false; for (int i = 0; i < Queue.queue.size(); i++) < if (Queue.queue.size() == 0) < System.out.println("Queue is empty"); isInQueue = false; break; >else if (Queue.queue.get(i).getNhsNumber() == p.getNhsNumber()) < System.out.println(p.getFirstName() + " is already in the queue (checkIfInQueue() method)"); isInQueue = true; break; >else < System.out.println(p.getFirstName() + " is not is the queue (checkIfInQueue() method)"); isInQueue = false; >> return isInQueue; >

Источник

Check if an object already exists in Java ArrayList

Then call queue.contains() to check if the queue contains the object.

Queue.queue.contains(p) // Call the contains method with the p object.

contains() will loop through the queue and check if the objects are equal to your p object by calling .equals() .

KvnH

Student of Software Development @ QUB

Comments

public boolean checkIfInQueue(Patient p) < // set nhsNumber equal to the nhsNumberLabel on the page String nhsNumber = nhsNumberLabel.getText(); System.out.println("Checking if " + nhsNumber + " already in the queue"); // create boolean to state whether a person is in the queue or not (defaults to false) boolean isInQueue = false; for (int i = 0; i < Queue.queue.size(); i++) < if (Queue.queue.size() == 0) < System.out.println("Queue is empty"); isInQueue = false; break; >else if (Queue.queue.get(i).getNhsNumber() == p.getNhsNumber()) < System.out.println(p.getFirstName() + " is already in the queue (checkIfInQueue() method)"); isInQueue = true; break; >else < System.out.println(p.getFirstName() + " is not is the queue (checkIfInQueue() method)"); isInQueue = false; >> return isInQueue; >

Источник

how to check if an object already exists

[font=Verdana][size=2]your question is not yet clear.[/size][/font]
[font=Verdana][size=2]In general we compare the instance of the object with null,[/size][/font]
[font=Verdana][size=2]to see if it exists or not. [/size][/font]

i have to write a flower shop
i need to check if a client already exists so that i dont add a new one

Well, read all about it in the API docs for the List.contains(. ) method.

ps. Bookmark The API docs or download them for easy reference.
Keep those docs at your fingertips whenever you want to write code.

[code]
if(klienci.contains(klient)) int index=klienci.indexOf(klient);

but it doesnt find the client in the list

[code]
if(klienci.contains(klient)) int index=klienci.indexOf(klient);

but it doesnt find the client in the list

if(klienci.contains(klient)) int index=klienci.indexOf(klient);

but it doesnt find the client in the list

When doing this, you’re looping through the list twice: once in the contains(. ) method, and another looptwhen using the indexOf(. ) method.
I suggest doing this:

i changed it to what You suggested but it doesnt change that it doesnt find the klient in the list
the client is added to the list when a button is clicked then that client adds to the cart but before he adds to the cart i need to check if it isnt a client that already exists if it is then return him with klient = klienci.get(index);

there is probably a better solution for that but unfortunately i can not think of one right one

Does your Klient class override the equals() and hashCode() methods?

Yes it should. Read all about it in the Object.equals() and Object.hashCode()
methods documentation.

By default equality is considered reference equality and you want value equality,
e.g. if two distinct objects contain identical member values you want to consider
the two distinct objects as equal.

if i define an equal method for klient (client in english) how shd i use it to compare if that client already exists cos i created a list of clients and i need to find that client in a list or shd i do in in some other way

can I see how you have defined the object variable?

Did you set it to null , initially?

if i define an equal method for klient (client in english) how shd i use it to compare if that client already exists cos i created a list of clients and i need to find that client in a list or shd i do in in some other way

That’s the convenient part of it all: the List does it for you when you call a
List.contains() of List.indexOf() method. Have a look at the contains() method:
(this is from the 1.6 JDK)

public boolean contains(Object o)
Iterator e = iterator();
if (o==null)
while (e.hasNext())
if (e.next()==null)
return true;
> else
while (e.hasNext())
if (o.equals(e.next()))
return true;
>
return false;
>

See how it uses the equals() method when it needs to find an object.

if i define method equals for klient how i can compare if that klient(client in english) already exists i created a list of clients client doesnt inherits from any other class so i can not compare it to a class it inherits from

if i define method equals for klient how i can compare if that klient(client in english) already exists i created a list of clients client doesnt inherits from any other class so i can not compare it to a class it inherits from

Your Klient class equals() method just needs to compare your ‘this’ Klient
with another Klient object:

Don’t forget to implement the hashCode() method too. The two methods always
come in pairs, if you implement one you have to implement the other one too.

If ‘nazwa’ and ‘pieniadze’ can be compared for equality using the ‘==’ operator,
I think all is fine. If one of them is an object (i.e. not a primitive) you have to
compare those members using the equals() method again (think about Strings).
Don’t forget to implement the hashCode() method too.

but i have a problem here cos when one button is clicked i create a client and add it to the list then when other button is clicked that client adds to the cart but the client created with the first button is not seen in the other portion of the code (the code for the second button)

but i have a problem here cos when one button is clicked i create a client and add it to the list then when other button is clicked that client adds to the cart but the client created with the first button is not seen in the other portion of the code (the code for the second button)

That’s an entirely different problem. Forget about GUIs for now and just take
care that your equals() and hashCode() methods are correctly implemented.
Build a little main() method that sticks Klients in a List and tries to find them
again afterwards. If all that works, build your GUI.

True, but my guess is that your equals() method doesn’t work yet and the less
circumstancial code around (such as buttons etc.) the less difficult it is to
debug your code. Note that a list can store duplicate objects (the equals()
method returns true) so you should test before adding:

. or you could use a Set for this but still then: your equals() method should
work correctly.

Источник