Determining input for Overloaded Method

I'm running into a bit of an issue with determining if the user input is an int or double.

Here's a sample:

public static int Square(int x)
{
    return x*x;
}

public static double Square(double x)
{
    return x*x;
}

I need to figure out how to determine based on the Scanner if the input is a int or double for the above methods. H开发者_如何学Cowever since this is my first programming class, I'm not allowed to use anything that hasn't been taught - which in this case, has been the basics.

Is there anyway of possibly taking the input as a String and checking to see if there is a '.' involved and then storing that into an int or double?

Lastly, I'm not asking for you to program it out, but rather help me think of a way of getting a solution. Any help is appreciated :)

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The Scanner has a bunch of methods like hasNextInt, hasNextDouble, etc. which tell you whether the "next token read by the Scanner can be interpreted as a (whatever)".

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Since you mentioned you've learned about the Scanner object, I assume the methods of that class are available to you for your use. In this case, you can detect if an input is an integer, double, or just obtain an entire line. The methods you would most be interested here would be the hasNextDouble() method (returns a boolean indicating whether or not the current token in the Scanner is actually a double or not) and the nextDouble() method (if the next token in the Scanner is in fact a double, parse it from the Scanner as one). This is probably the best direction for determining input types from a file or standard input.

Another option is to use the wrapper classes static methods for converting values. These are generally named like Integer.parseInt(str) or Double.parseDouble(str) which will convert a given String object into the appropriate basic type. See the Double classes method pasrseDouble(String s) for more details. It could be used in this way:

String value = "123.45"
double convertedValue = 0.0;

try {
    convertedValue = Double.parseDouble(value);
} catch (NuberFormatException nfe) {
    System.err.println("Not a double");
}

This method is probably best used for values that exist within the application already and need to be verified (it would be overkill to construct a Scanner on one small String for this purpose).

Finally, yet another potential (but not very clean, straightforward, or probably correct technique) could be looking at the String object directly and trying to find if it contains a decimal point, or other indicators that it is in fact a double. You may be able to use indexOf(String substr) to determine if it appears in the String ever. I suspect this method has a lot of potential problems though (say for example, what if the String has multiple '.' characters?). I wouldn't suggest this route because it is error prone and hard to follow. It might be an option if that's what the constraints are, however.

So, IMHO, your options should go as follow:

1. Use the Scanner methods hasNextDouble() and nextDouble()
2. Use the wrapper class methods Double.parseDouble(String s)
3. Use String methods to try and identify the value (avoid this technique at all costs if either of the above options are available).

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Since you think you won't be allowed to use the Scanner methods there are a number of alternatives you try. You mentioned checking to see if a String contains a .. To do this you could use the contains method on String.

"Some words".contains("or") // evaluates to true

The problem with this approach is that there are many Strings that contain . but aren't floating point numbers. For examples, sentences, URLs and IP addresses. However, I doubt you're lecturer is trying to catch you out with and will probably just be giving you ints and doubles.

So instead you could try casting. Casting a double to an int results in the decimal portion of the number being discarded.

double doubleValue = 2.7;

int castedDoubleValue = (int) doubleValue; // evaluates to 2

double integerValue = 3.0;

int castedIntegerValue = (int) integerValue; // evaluates to 3

Hopefully, that should be enough to get you started on writing a solution to the problem.

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Can be checked like this

            if(scanner.hasNextDouble()}
            {
               System.out.println("Is double");
            }


            if(scanner.hasNextDouble()}
            {
              System.out.println("Is double");
            }