What is the list interface in Java 11?
What is the list interface in Java 11?
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In Java 11, a List interface represents a collection of objects that can be accessed by their index. This interface extends the Collection interface and is implemented by several classes, including ArrayList, LinkedList, and Vector.
The List interface provides various methods for manipulating the list elements. Some of the most commonly used methods include:
add(E e): This method adds a specified element at the end of this list. addAll(Collection<? extends E> c): This method inserts all of the elements in the specified collection into this list, starting at the specified position. clear(): This method removes all elements from this list. contains(Object o): This method returns true if this list contains the specified element. containsAll(Collection<?> c): This method returns true if this list contains all of the elements in the specified collection. get(int index): This method returns the element at the specified position in this list. indexOf(Object o): This method returns the index of the first occurrence of the specified element in this list, or -1 if it is not found. isEmpty(): This method returns true if this list has no elements. iterator(): This method returns an iterator over the elements in this list. lastIndexOf(Object o): This method returns the index of the last occurrence of the specified element in this list, or -1 if it is not found. listIterator(): This method returns a list iterator over the elements in this list (in proper sequence). listIterator(int index): This method returns a list iterator over the element at the specified position in this list, in proper sequence. remove(Object o): This method removes the first occurrence of the specified element from this list. removeAt(int index): This method removes the element at the specified position in this list. set(int index, E e): This method sets the element at the specified position in this list. size(): This method returns the number of elements in this list. subList(int fromIndex, int toIndex): This method returns a view of the portion of this list between the specifiedfromIndex and toIndex, inclusive. toArray(): This method returns an array containing all of the elements in this list in proper sequence. toArray(IntFunction mapFn): This method returns an array containing all of the elements in this list in proper sequence, where each element is transformed by the provided mapping function. toString(): This method returns a string that contains the name of the class of objects contained within this List, the size (length) of the List, and the elements themselves, enclosed in "][" characters.
In summary, the Java List interface provides a variety of methods for managing collections of objects in a program. It is an essential part of the Java Collections Framework and is widely used in Java programming.
What are interface methods in Java?
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Interface methods in Java refer to the methods declared within an interface, which is a abstract construct that defines a contract or a blueprint of behavior for any class that implements it. An interface cannot be instantiated on its own, but rather serves as a way to define a set of methods that must be implemented by any class that inherits from it.
Interface methods are essentially the same as abstract methods in abstract classes, with one key difference: an abstract class can have both abstract and concrete (i.e., fully implemented) methods, whereas an interface can only have abstract methods. This means that any class implementing an interface must provide its own implementation for each of the interface's methods.
Here are some key characteristics of interface methods:
Abstract: Interface methods are abstract by definition, meaning they don't have a body and cannot be called directly. Instead, you need to create an implementation in a concrete subclass that extends or implements the interface. Must be implemented: Any class implementing the interface must provide its own implementation for each of the interface's methods. If a class fails to implement all the required methods, it will not compile. No constructor: Interfaces do not have constructors, as they are abstract and cannot be instantiated directly. Multiple inheritance: A class can implement multiple interfaces, which allows for multiple "inheritance" paths. This is different from Java's single inheritance model for classes.Interface methods are useful in several scenarios:
Defining a common contract: Interfaces help define a shared contract or set of behaviors that must be implemented by any class that inherits from it. Promoting abstraction: By declaring abstract methods, interfaces promote abstraction and decouple the interface's implementation details from its public API. Enforcing consistency: When multiple classes implement an interface, they are forced to adhere to a consistent set of behaviors, which can be beneficial for code maintainability and reusability.In summary, interface methods in Java define a contract or blueprint of behavior that must be implemented by any class that inherits from the interface. They provide a way to promote abstraction, enforce consistency, and define a common contract among classes that implement the same interface.
