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POcorrect way to check user input with scanner
 

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    <p>I'm very new to programming, I've wrote an app for working the area out of certain shapes.</p> <p>I have the <code>AreaCalculations</code> in another class can provide if needed but that works fine.</p> <p>My problem is checking when the user types a character instead of a double. As you can see from my code i got it to work by using a while loop and <code>(!reader.NextDouble())</code> .</p> <p>This works but i then have to repeat the question. I could do this throughout the program but is there an easier/tidier way of doing this???</p> <p>Thanks,</p> <p>Craig </p> <p>My code so far :</p> <pre><code>package areaprog; import java.util.Scanner; public class Mainprog { public static void main (String [] args){ //Area Menu Selection System.out.println("What shape do you need to know the area of?\n" + "1: Square?\n" + "2: Rectangle?\n" + "3: Triangle?\n" + "4: Circle? \n" + "5: Exit\n" ); //User input for menu Scanner reader = new Scanner(System.in); System.out.println("Number: "); //Menu syntax checking while (!reader.hasNextDouble()) { System.out.println("Thats not a number you tool.\n"); System.out.println("Now pick again\n" + "1: Square?\n" + "2: Rectangle?\n" + "3: Triangle?\n" + "4: Circle? \n" + "5: Exit\n" ); reader.next(); //ask for next token? } double input = reader.nextDouble(); reader.nextLine(); //Depending on user selection, depends on what method is called using switch. Scanner scan = new Scanner(System.in); //Square selection if (input == 1){ System.out.println("What is a length of 1 side of the Square?\n"); double s1 = scan.nextDouble(); double SqAns = AreaCalculator.getSquareArea(s1); System.out.println("The area of you square is: " + SqAns); } //Rectangle selection if (input == 2){ System.out.println("What is the width of your rectangle?.\n"); double r1 = scan.nextDouble(); System.out.println("What is the height of your rectangle?\n"); double r2 = scan.nextDouble(); double RecAns = AreaCalculator.getRectArea(r1, r2); System.out.println("The area of your rectangle is: " + RecAns); } //Triangle selection if (input == 3){ System.out.println("What is the base length of the triangle?."); double t1 = scan.nextDouble(); System.out.println("What is the height of your triangle?"); double t2 = scan.nextDouble(); double TriAns = AreaCalculator.getTriArea(t1, t2); System.out.println("The area of your triangle is " + TriAns); } //Circle selection if (input == 4){ System.out.println("What is the radius of your circle?."); double c1 = scan.nextDouble(); double CircAns = AreaCalculator.getCircleArea(c1); System.out.println("The area of your circle is " + CircAns); } //Exit application if (input == 5){ System.out.println("Goodbye."); } } } </code></pre> <p>Ok so I've added in a Exception to catch the error. So its a bit cleaner now in the way it handles people not using intergers.</p> <p>Number: 1 What is a length of 1 side of the Square?</p> <p>a Why are you trying to be clever? use an interger.</p> <p>But then the program just ends.... How would i either get them back to the main menu or even get them to re-input there last effort?</p> <p>Thanks,</p> <p>Craig</p>
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