What is list of objects in Java?

The List interface in Java provides a way to store the ordered collection. It is a child interface of Collection. It is an ordered collection of objects in which duplicate values can be stored . Since List preserves the insertion order, it allows positional access and insertion of elements.

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What are objects types in Java?

Object Data Type: These are also referred to as Non-primitive or Reference Data Type. They are so-called because they refer to any particular objects. Unlike the primitive data types, the non-primitive ones are created by the users in Java. Examples include arrays, strings, classes, interfaces etc .

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When should I define a class?

As a rule of thumb, when you have a set of data with a specific structure and you want to perform specific methods on it , use a class. That is only valid, however, if you use multiple data structures in your code. If your whole code won’t ever deal with more than one structure.

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What does .class extension mean in Java?

Definition and Usage The extends keyword extends a class (indicates that a class is inherited from another class ). In Java, it is possible to inherit attributes and methods from one class to another. We group the “inheritance concept” into two categories: subclass (child) – the class that inherits from another class.

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