Java, how to compare Strings with String Arrays

问题:

I have been searching here for some time but haven't been able to find the answer to it.

I am basically required to use an array for this assignment from college. And then I am supposed to check that the input (which is also a String) matches whatever's stored within the String array.

I know one can easily compare Strings by using the .equals() method. However, the same method is not working with the String array.

I created the following example of code for the purpose of StackOverflow so you can use it to explain it to me, if you'd like.

What am I doing wrong?

import java.util.Scanner;

class IdiocyCentral {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        /*Prints out the welcome message at the top of the screen*/
        System.out.printf("%55s", "**WELCOME TO IDIOCY CENTRAL**\n");
        System.out.printf("%55s", "=================================\n");

        String [] codes = {"G22", "K13", "I30", "S20"};

        System.out.printf("%5s%5s%5s%5s\n", codes[0], codes[1], codes[2], codes[3]);
        System.out.printf("Enter one of the above!\n");

        String usercode = in.nextLine();

        if (codes.equals(usercode)) {
            System.out.printf("What's the matter with you?\n");
        }
        else {
            System.out.printf("Youda man!");
        }

    }
}

I apologize if this has been asked before and I just missed it, if its a double question, I will remove it.

回答1:

I presume you are wanting to check if the array contains a certain value, yes? If so, use the contains method.

if(Arrays.asList(codes).contains(userCode))

回答2:

Right now you seem to be saying 'does this array of strings equal this string', which of course it never would.

Perhaps you should think about iterating through your array of strings with a loop, and checking each to see if they are equals() with the inputted string?

...or do I misunderstand your question?

回答3:

Iterate over the codes array using a loop, asking for each of the elements if it's equals() to usercode. If one element is equal, you can stop and handle that case. If none of the elements is equal to usercode, then do the appropriate to handle that case. In pseudocode:

found = false
foreach element in array:
  if element.equals(usercode):
    found = true
    break

if found:
  print "I found it!"
else:
  print "I didn't find it"

回答4:

If I understand your question correctly, it appears you want to know the following:

How do I check if my String array contains usercode, the String that was just inputted?

See here for a similar question. It quotes solutions that have been pointed out by previous answers. I hope this helps.

回答5:

Instead of using array you can use the ArrayList directly and can use the contains method to check the value which u have passes with the ArrayList.