First, last and sometime middle name detection Java

问题

I am trying to write a code to give off the user's name in different formats after they enter it. However, if a user does not have a middle name, the system should print that there was an error. I have it so it works perfectly if the user enters three names but does not work if the user enters two names. Here is my code:

import java.util.Scanner;

public class Assignment3 
{
  public static void main(String[] args) 
  {
    String fullName;
    Scanner in = new Scanner(System.in);
    System.out.print ("What are your first, middle, and last names? ");
    fullName = in.nextLine();
    System.out.println(fullName);
    if (fullName.contains(" "))
    {
      String[] nameParts = fullName.split(" ");
      String firstInitial = nameParts[0].substring(0,1).toUpperCase();
      String secondInitial = nameParts[1].substring(0,1).toUpperCase();
      String thirdInitial = nameParts[2].substring(0,1).toUpperCase();

      if (nameParts[2].isEmpty())
      {
        System.out.println("No Middle Name Detected");
      }
      else
      {
        System.out.println ("Your initials are: " + firstInitial + secondInitial + thirdInitial);

        String lastVariationOne = nameParts[2].substring(0, nameParts[2].length());
        lastVariationOne = lastVariationOne.toUpperCase();
        String firstVariationOne = nameParts[0].substring(0, nameParts[0].length());
        firstVariationOne = firstVariationOne.substring(0,1).toUpperCase() + firstVariationOne.substring(1, nameParts[0].length());
        System.out.println("Variation One: " + lastVariationOne + ", " + firstVariationOne + " " + secondInitial + ".");

        String lastVariationTwo = nameParts[2].substring(0, nameParts[2].length());
        lastVariationTwo = lastVariationTwo.substring(0,1).toUpperCase() + lastVariationTwo.substring(1, nameParts[2].length());
        System.out.println("Variation Two: " + lastVariationTwo + ", " + firstVariationOne);
      }
    }
    else
    {
      System.out.println("Wrong. Please enter your name properly.");
    }
  }
}

回答1:

Instead of this:

if (nameParts[2].isEmpty())
{
    System.out.println("No Middle Name Detected");
}

something like

if(nameParts.length != 3)
{
    System.out.println("Invalid entry");
}

might be preferrable.

Basically, in the case that there are only two names entered, split() will return an array of length 2, whose elements are accessible by indices 0 and 1.

But in your if condition you attempt to access index 2, which could be out of bounds (it would be OOB for the case where you entered only two names).

To resolve this, you could either (a) try it like you do, but catch the ArrayIndexOutOfBoundsException or (b) check first that split produced a properly sized array, then go from there (this was the approach I took with the change I listed).

I'd suggest (b), but both approaches seem fine.

回答2:

If you don't input middlename, would the array size be 2? So there is NO namespart[2]. Just check size of namespart. @jedwards jedwards's solution is there.

来源：https://stackoverflow.com/questions/18883130/first-last-and-sometime-middle-name-detection-java

标签

java

split

java.util.scanner