How does switch rules vs statements behave in multithreaded code?

In Java, the behavior of switch statements and switch expressions can vary significantly, especially in a multithreaded environment. It's important to understand how concurrent access and thread safety can affect the control flow of your code.

Switch Statements

A switch statement evaluates a variable and executes code blocks based on its value. However, when used in a multithreaded context, race conditions may occur if multiple threads modify shared state that the switch statement evaluates. This can lead to unpredictable behavior.

Switch Expressions

Switch expressions, introduced in Java 12, provide a safer alternative to switch statements. They return a value and can be more concise. In a multithreaded environment, switch expressions can be used with care to minimize side effects, but shared mutable state can still introduce issues.

Example

class Example {
    private int state = 0;

    public void execute() {
        switch (state) {
            case 0:
                System.out.println("State is 0");
                break;
            case 1:
                System.out.println("State is 1");
                break;
            default:
                System.out.println("State is unknown");
                break;
        }
    }

    public void setState(int newState) {
        this.state = newState;
    }
}