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Java Java Objects Delivering the MVP Applying a Discount Code

Paramvir Singh
Paramvir Singh
1,517 Points

How do I check if the user has entered a String or not?

In one of the Tasks I was supposed to check if the user has entered a String or not, but I couldn't figure it out. I even looked at the Java API but still coundn't find anything.

Order.java
public class Order {
  private String itemName;
  private int priceInCents;
  private String discountCode;

  public Order(String itemName, int priceInCents) {
    this.itemName = itemName;
    this.priceInCents = priceInCents;
  }

  private  String normalizeDiscountCode (String d ) {
    if ( true ) {
      throw new IllegalArgumentException("Invalid discount code.");
    }
    this.discountCode = d.toUpperCase();
    return this.discountCode;
  }

  public String getItemName() {
    return itemName;
  }

  public int getPriceInCents() {
    return priceInCents;
  }

  public String getDiscountCode() {
    return discountCode;
  }

  public void applyDiscountCode(String discountCode) {
    this.discountCode = normalizeDiscountCode( discountCode );
  }
}
Example.java
public class Example {

  public static void main(String[] args) {
    // This is here just for example use cases.

    Order order = new Order(
            "Yoda PEZ Dispenser",
            600);

    // These are valid.  They are letters and the $ character only
    order.applyDiscountCode("abc");
    order.getDiscountCode(); // ABC

    order.applyDiscountCode("$ale");
    order.getDiscountCode(); // $ALE


    try {
      // This will throw an exception because it contains numbers
      order.applyDiscountCode("ABC123");
    } catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"
    }
    try {
      // This will throw as well, because it contains a symbol.
      order.applyDiscountCode("w@w");
    }catch (IllegalArgumentException iae) {
      System.out.println(iae.getMessage());  // Prints "Invalid discount code"
    }

  }
}

1 Answer

Kevin Grifo
Kevin Grifo
9,824 Points

Hi Paramvir,

You could use the instanceof operator to check if a specific object is a String. The java instanceof operator is used to test whether the object is an instance of the specified type (class or subclass or interface).

An example would be

String foo = "this Is a String"; //Checking if foo is of type string if( foo instanceof String ) { // do something String related to foo System.out.println("foo is a string!"); }

I hope this helps.