How many interfaces are there in a collection in java with example

Aimee 109 Published: 10/14/2024

How many interfaces are there in a collection in java with example

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In Java, a collection is an object that stores multiple values and provides operations to manipulate those values. A collection can have various types of interfaces, each serving a specific purpose. Here are some common interfaces in a collection with examples:

List Interface: This interface represents a sequence or linear collection of objects. It allows you to access elements by their index (position).

Example:

import java.util.ArrayList;

import java.util.List;


public class Main {


public static void main(String[] args) {


List colors = new ArrayList<>();


colors.add("Red");


colors.add("Green");


colors.add("Blue");


System.out.println("Colors list: " + colors);


// Accessing elements by index


String firstColor = colors.get(0); // prints "Red"


}


}
Set Interface: This interface represents a collection of unique objects, meaning no duplicates are allowed.

Example:

import java.util.HashSet;

import java.util.Set;


public class Main {


public static void main(String[] args) {


Set colors = new HashSet<>();


colors.add("Red");


colors.add("Green");


colors.add("Blue");


System.out.println("Colors set: " + colors);


// No duplicates allowed


colors.add("Blue"); // does not add the duplicate value


}


}
Map Interface: This interface represents a collection of key-value pairs, where each unique key maps to a specific value.

Example:

import java.util.HashMap;

import java.util.Map;


public class Main {


public static void main(String[] args) {


Map<String, String> countries = new HashMap<>();


countries.put("USA", "United States");


countries.put("UK", "United Kingdom");


System.out.println("Countries map: " + countries);


// Retrieving values by keys


String countryName = countries.get("USA"); // prints "United States"


}


}
Queue Interface: This interface represents a collection that follows the FIFO (First-In-First-Out) principle.

Example:

import java.util.LinkedList;

import java.util.Queue;


public class Main {


public static void main(String[] args) {


Queue messages = new LinkedList<>();


messages.add("Hello");


messages.add("World");


System.out.println("Messages queue: " + messages);


// Retrieving the first element


String message = messages.poll(); // prints "Hello"


}


}
Stack Interface: This interface represents a collection that follows the LIFO (Last-In-First-Out) principle.

Example:

import java.util.Stack;

public class Main {


public static void main(String[] args) {


Stack messages = new Stack<>();


messages.push("Hello");


messages.push("World");


System.out.println("Messages stack: " + messages);


// Retrieving the top element


String message = messages.pop(); // prints "World"


}


}

These are some of the most common interfaces in a Java collection. Each interface has its own specific use cases and is suited for different types of data storage and manipulation.

How many types of interfaces are there in Java?

I'd be happy to help!

In the world of Java programming, interfaces play a crucial role in defining the behavior and structure of an object-oriented program. An interface is a abstract construct that defines a contract or a protocol for its implementations. It's like a blueprint or a set of instructions on how to behave.

Now, let's talk about the different types of interfaces in Java! There are several types, but I'll cover at least 10:

Functional Interface: A functional interface is an interface that has exactly one abstract method (SAM). These interfaces can be used as lambda expressions or method references. Think of them like a mini-program within your program.

Example: java.util.function.Predicate<T> is a functional interface that takes in an input and returns a boolean value indicating whether the input meets certain criteria.

Marker Interface: A marker interface is simply an empty interface with no methods or fields. Its sole purpose is to identify objects that implement this interface, usually for some specific functionality or attribute.

Example: java.lang.Cloneable is a marker interface used to indicate that an object can be cloned.

Pure Virtual Interface (PVI): A PVI is an interface with no concrete methods and only abstract methods. It provides a blueprint for other interfaces or classes to follow.

Example: java.awt.print.PrinterJob has no concrete methods, but it's a PVI because its implementations must provide their own logic.

Concrete Interface: A concrete interface is one that has at least one concrete method (i.e., not abstract). These interfaces can be implemented directly or extended by other interfaces or classes.

Example: java.lang.Runnable has a single concrete method run(), which is meant to be overridden by its implementations.

Abstract Interface: An abstract interface is an interface with only abstract methods, meaning they must be implemented by any class that implements the interface.

Example: java.awt.print.Pageable has several abstract methods related to printing pages.

Composite Interface: A composite interface combines multiple interfaces into a new interface, allowing for easier reuse and inheritance.

Example: java.sql.Statement is an interface that inherits from both java.sql.PreparedStatement and java.sql.ResultSet.

Tagged Interface: A tagged interface is one where you can use Java's annotation system to attach metadata or tags to the interface itself or its methods.

Example: javax.persistence.Entity is a tagged interface used in JPA (Java Persistence API) to identify an entity bean.

Parameterized Interface: A parameterized interface is one that takes one or more type parameters, similar to Java generics.

Example: java.util.Map<K, V> is a parameterized interface for maps, where K represents the key type and V represents the value type.

Multicast Interface: A multicast interface allows multiple classes to implement the same method signature with different implementations.

Example: java.awt.event.MouseListener has several methods (like mouseClicked()) that can be implemented differently by various mouse listener classes.

Extension Interface: An extension interface is one that provides default or template code for its implementations, which can then customize it as needed.

Example: javax.swing.table.TableModel has abstract methods and some implementation-specific logic, allowing custom models to inherit from this interface.

These are just a few of the many types of interfaces in Java. Understanding each type's unique characteristics will help you write more effective and reusable code.

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