Checking Character in a String using .equals() not working

Question

I'm trying to check if a letter submitted by user is contained in a string, but it always return false. From what I read the .equals() function should work. I was expecting that if a user inputs the letter "a" it would return "pass" if the string was "america".

 for (int i = 0; i < outputTest.length(); i++){
                    if (userInput.equals(outputTest.charAt(i))){
                        System.out.println("Pass");
                    }else {
                        System.out.println("Fail");
                    }
                }

http://stackoverflow.com/questions/7520432/what-is-the-difference-between-vs-equals-in-java — mika, Oct 20 '16 at 23:07
Send me your outputTest variable.. i mean what is it contains ? — KuldeeP ChoudharY, Oct 20 '16 at 23:09
Use `outputTest.substring(i, i + 1)` instead of `outputTest.charAt(i)`. — , Oct 20 '16 at 23:13

Pshemo · Accepted Answer · 2016-10-20T23:21:12.163

Based on outputTest.length() and outputTest.charAt() I am assuming that outputTest is String.
Based on userInput.equals I am assuming it is not primitive type like char (since primitive types don't have methods). It is also not Character, otherwise you would see Pass few times. So it most likely is also String.

outputTest.charAt(i) returns char, but you are comparing it with String which equals method looks like:

964  public boolean equals(Object anObject) {
965      if (this == anObject) {
966          return true;
967      }
968      if (anObject instanceof String) {
969          String anotherString = (String)anObject;
970          int n = value.length;
971          if (n == anotherString.value.length) {
972              char v1[] = value;
973              char v2[] = anotherString.value;
974              int i = 0;
975              while (n-- != 0) {
976                  if (v1[i] != v2[i])
977                      return false;
978                  i++;
979              }
980              return true;
981          }
982      }
983      return false;
984  }

So since equals expects Object, char (returned from outputTest.charAt(i)) will be automatically boxed to Character, but since Character doesn't extend String test

if (anObject instanceof String)

will fail and you will immediately move to return false;.

You may want to use contains method if you want to check if one String contains another

outputTest.contains(userInput)

score 1 · Answer 2 · answered Oct 20 '16 at 23:29

1

To find a string in another string, just do:

return text.contains(string);

To find a char in a string, do

return text.indexOf(ch) > -1;

answered Oct 20 '16 at 23:29

Daniel Rodriguez

607
6
11

score 0 · Answer 3 · answered Oct 20 '16 at 23:19

0

What is the data type of your object userInput? You seem to be comparing a String object with a character which is returned by the charAt() method. That will always return false.

answered Oct 20 '16 at 23:19

Bala_G

1
1

Bruce Lin · Answer 4 · 2016-10-21T00:20:51.597

When you are learning to use methods, a good habit to develop is to look at what kind of data type the methods apply or return. For instance, you cannot code this: char scanner.nextLine() // nextLine() is to read String, not char. Therefore, in your code outputTest.charAt(i) // I am a char, and this userInput.equals() // I am a String, you are comparing different things. You cannot compare an apple with a desk because they are two different objects. The compiler will always tell you false.

I assume: String inputTest = scanner.nextLine(); for user input a letter, and you can consider "a" as a String with a length 1. (or any other letters inside)

    if (outputTest.contains(userInput)) // now you are comparing String and String
       System.out.println("Pass");
    else
       System.out.println("Fail");

Checking Character in a String using .equals() not working

4 Answers4