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Java 21 Features

Java 21 Features


Switch Expressions

Java 21 introduces a simplified syntax for switch statements, allowing them to be used as expressions. This enables more concise and readable code.

Example Code:

int day = 3;
String dayType = switch (day) {
    case 1, 2, 3, 4, 5 -> "Weekday";
    case 6, 7 -> "Weekend";
    default -> throw new IllegalArgumentException("Invalid day: " + day);
};
System.out.println("Day type: " + dayType);

Pattern Matching for instanceof

Java 21 introduces pattern matching for the instanceof operator, allowing for more concise and readable code when working with object types.

Example Code:

Object obj = "Hello";
if (obj instanceof String s) {
    System.out.println("Length of string: " + s.length());
} else {
    System.out.println("Not a string");
}

Records

Java 21 introduces record classes, which are a concise way to declare classes that are essentially data carriers, automatically generating constructors, accessors, and equals() and hashCode() methods.

Example Code:

public record Person(String name, int age) {
    // Record class automatically defines:
    // - Constructor
    // - Accessor methods
    // - equals() and hashCode() methods
}

Text Blocks

Java 21 introduces text blocks, which allow for multiline string literals without the need for escape characters. This improves readability and maintainability of code.

Example Code:

String html = """
              <html>
              <body>
              <p>Hello, world!</p>
              </body>
              </html>
              """;
System.out.println(html);

Sealed Classes

Java 21 introduces sealed classes, which restrict the subclasses that can extend or implement them, providing more control over class hierarchies.

Example Code:

public sealed interface Shape permits Circle, Rectangle, Triangle {
    // Interface definition
}

Local Interfaces

Java 21 allows the declaration of interfaces within methods, known as local interfaces. This can be useful for encapsulating functionality within a method.

Example Code:

public void process() {
    interface Callback {
        void onSuccess();
        void onFailure();
    }
    // Local interface usage
}

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