Pattern Matching for switch Statements

Pattern Matching for switch Statements is a new feature introduced in Java 18 that allows developers to use patterns as case labels in switch statements. This feature was first introduced as a preview feature in Java 14 and was further improved in Java 15 and Java 17 before being made a permanent feature in Java 18.

Prior to Java 18, switch statements could only use primitive types, enums, and strings as case labels. With pattern matching, developers can now use patterns, which are more flexible and powerful than simple literals. Patterns allow developers to match against more complex conditions, such as types, values, and structures.

Here's an example of how pattern matching works:

public String getAnimalSound(Animal animal) {

    String sound = switch (animal) {

        case Cat c -> "Meow";

        case Dog d -> "Woof";

        case Lion l -> "Roar";

        default -> throw new IllegalArgumentException("Unknown animal: " + animal);

    };

    return sound;

}

In this example, the switch statement uses pattern matching to match against different types of animals. The cases use the -> operator to specify the pattern to match against and the corresponding code to execute if the pattern matches. The default case is used to handle any animals that do not match any of the previous cases.

Here are some of the patterns that can be used in switch statements:

Type Patterns: match against a specific type or its subtypes.

Value Patterns: match against specific values, ranges, or sets of values.

Object Patterns: match against the state of an object, such as its fields or methods.

Binding Patterns: introduce a new variable and match against its value.

Pattern Matching for switch Statements can simplify code and make it more expressive and readable. It can also reduce the need for if-else statements and other conditional logic. However, it's important to use pattern matching judiciously and not overuse it, as it can make code more complex if used improperly.