How many types of interfaces are there in Java?

How many types of interfaces are there in Java?

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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:

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.

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

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

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

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

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

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

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

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

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.

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:

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"
}
}

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
}
}

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"
}
}

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"
}
}

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.