![]() ![]() This custom exception doesn't provide any extra information e.g. ![]() Public class DuplicateIDException extends Exception ![]() If you use someone else's exceptions, will users have access to those exceptions? A similar question is, should your package be independent and self-contained?Ĭustom Exception or Custom Message with Standard Exception?įor example if you declare an Exception that doesn't provide any useful information other than a custom name then it probably uses generic Exception class with a custom message as shown in below example:.Does your code throw more than one related exception?.Would it help users if they could differentiate your exceptions from those thrown by classes written by other vendors?.Do you need an exception type that isn't represented by those in the Java platform?.package. should write your own exception classes if you answer yes to any of the following questions otherwise, you can probably use someone else's. You can have as many attributes as a key for the HashMap. In the below example, two attributes – title and author – will be used together as a single key for the HashMap. This class has two fields or attributes – title and author. This class will be used as a key in the HashMap. PrerequisitesĬreate below Book class that overrides equals() and hashCode() methods. So in situations, where you need to use custom object as a key in HashMap then you can use this example. Most of the time you generally use Java API provided classes, for example, mostly String objects as keys for HashMap. To use user defined objects as keys in Map you need to tell Java how to compare user defined objects by overriding the hashCode() and equals() methods. In custom object as a key in HashMap example, I will show you how to work with user defined objects as keys in Map. In this Java HashMap example I am going to tell you how to use custom object as a key in HashMap. ![]()
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