Java 17 Features

 Some of the new features and improvements introduced in Java 17 include:

1. Sealed Classes: Sealed classes provide a way to limit the implementation of a class to a specific set of classes or interfaces, making it easier to enforce contracts and reduce the risk of errors.

2. Records: Records provide a compact and easy-to-use syntax for declaring simple data classes that represent an immutable value.

3. Pattern Matching for instanceof: Java 17 introduces pattern matching for the instanceof operator, making it easier to write type-safe and concise code.

4. Improved Concurrency: Java 17 includes several improvements to the Java concurrency API, including the addition of new classes and methods to simplify the development of concurrent applications.

5. Text Blocks: Java 17 includes text blocks, a new feature that makes it easier to work with multi-line string literals in your code.

6. Foreign Linker API: Java 17 introduces the Foreign Linker API, which provides a way to link native code and libraries directly into a Java program, improving the performance and integration of Java applications with native code.

Here is the example of sealed class

sealed interface Shape permits Circle, Rectangle { }

final class Circle implements Shape {

    private final double radius;

    public Circle(double radius) {

        this.radius = radius;

    }

    public double getRadius() {

        return radius;

    }

}

final class Rectangle implements Shape {

    private final double length;

    private final double width;

    public Rectangle(double length, double width) {

        this.length = length;

        this.width = width;

    }

    public double getLength() {

        return length;

    }

    public double getWidth() {

        return width;

    }

}

In this example, Shape is a sealed interface that permits the classes Circle and Rectangle to implement it. This means that no other classes can implement the Shape interface. By using sealed classes, you can restrict the types that can implement an interface and ensure type safety in your code.

Java Records is a new feature introduced in Java 16 that provides a compact syntax for declaring classes that are purely transparent data carriers. Records are a way to define simple data classes that have a private final field for each component, a public constructor, and automatically generated accessor methods (getters), equals, hashCode and toString methods.

Here is an example of how you could define a Person record in Java:

record Person(String name, int age) { }

This record definition is equivalent to the following class definition:

class Person { private final String name; private final int age; public Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; return age == person.age && Objects.equals(name, person.name); } @Override public int hashCode() { return Objects.hash(name, age); } @Override public String toString() { return "Person{" + "name='" + name + '\'' + ", age=" + age + '}'; } }

With records, you can define data classes in a more concise and readable way, while still having the benefits of automatically generated accessor methods, equals, hashCode, and toString methods.

Pattern matching in Java is a new feature introduced in Java 16/17 that provides a more concise and type-safe way to perform type checking and extract values from objects. With pattern matching, you can use the instanceof operator in a switch expression to match objects against a specific pattern and extract values from the matched object.

Here's an example of how you could use pattern matching in a switch expression to match an object against a specific type and extract values from the matched object:

public static void printArea(Shape shape) {

    switch (shape) {

        case Circle c:

            System.out.println("The area of the circle is " + Math.PI * c.getRadius() * c.getRadius());

            break;

        case Rectangle r:

            System.out.println("The area of the rectangle is " + r.getLength() * r.getWidth());

            break;

        default:

            System.out.println("Unknown shape");

            break;

    }

}

In this example, the printArea method takes a Shape object as an argument and uses a switch expression to match the object against specific patterns. If the object is a Circle object, the radius is extracted and used to calculate the area. If the object is a Rectangle object, the length and width are extracted and used to calculate the area. If the object is not a Circle or a Rectangle, the default case is executed and an "Unknown shape" message is printed.

Pattern matching provides a more concise and type-safe way to perform type checking and extract values from objects, and can make your code more readable and maintainable.

In Java, pattern matching is performed using the instanceof operator in a switch expression. The instanceof operator is used to check the type of an object and determine whether it matches a specified pattern.

Here's an example of how you could use the instanceof operator in a switch expression to match an object against a specific type and extract values from the matched object:

public static void printArea(Object shape) { if (shape instanceof Circle) { Circle c = (Circle) shape; System.out.println("The area of the circle is " + Math.PI * c.getRadius() * c.getRadius()); } else if (shape instanceof Rectangle) { Rectangle r = (Rectangle) shape; System.out.println("The area of the rectangle is " + r.getLength() * r.getWidth()); } else { System.out.println("Unknown shape"); } }

In this example, the printArea method takes an Object object as an argument and uses the instanceof operator in an if-else statement to check the type of the object. If the object is a Circle object, the radius is extracted and used to calculate the area. If the object is a Rectangle object, the length and width are extracted and used to calculate the area. If the object is not a Circle or a Rectangle, the else case is executed and an "Unknown shape" message is printed.

The instanceof operator can be useful for performing type checking and extracting values from objects, but it can also lead to code that is verbose and harder to maintain. The introduction of pattern matching in Java 16 provides a more concise and type-safe way to perform type checking and extract values from objects.