Question

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How do I compare strings in Java?

I am having trouble understanding how to use a Java switch statement. After executing a method in one of the case statements, it still then goes to the default statement and runs that too. Here’s the code:

Scanner scanner = new Scanner(System.in);
String option = null;

while (option != "5") {
    ShowMenu();
    option = scanner.nextLine();
    switch (option) {
        case "1": ViewAllProducts(); break;
        case "2": ViewProductDetails(scanner); break;
        case "3": DeleteProduct(scanner); break;
        case "4": AddProduct(scanner); break;
        case "5": break;
        default: System.out.println("Invalid option. Please try again."); break;
    }
}

The above code is in the main method. After running case “4” for example, it prints “Invalid option.”

Answer 1

I am modifying your code to re-initialize your scanner reference before reading new option..

    Scanner scanner = new Scanner(System.in);
    String option = null;

    ShowMenu();
    option = scanner.nextLine();

    while (!"5".equals(option)) {
        switch (option) {
            case "1": ViewAllProducts(); break;
            case "2": ViewProductDetails(scanner); break;
            case "3": DeleteProduct(scanner); break;
            case "4": AddProduct(scanner); break;
            case "5": break;
            default: System.out.println("Invalid option. Please try again..."); break;
        }
        ShowMenu();
        scanner = new Scanner(System.in);  // Add this here

        option = scanner.nextLine();    // Use brand new scanner without any problem..
    }

Rest, you can read from the link I provided, to know the difference between various methods for reading user input..