Question

I am trying to use a for loop to examine every character in a single dimensional string array and print “Character [a] is uppercase” or “Character [b] is lowercase” or “Character [c] is a space.” I also have to print the index number and the character in that index.

I thought I was supposed to create separate strings with uppercase letters and lowercase letters but turns out I was wrong. I also don’t know if I’m supposed to convert the string array into a char array?

I think I’m supposed to use charAt() method but I don’t know how.

This is what I had done:

for(x = 0; x < fullName.length(); x++)
{
    if(fullName[0] == nameUpperCase[2]);
    {
        System.out.print("character [0] located at position [0] is  lowercase");
    }

    if(fullName[1] == nameLowerCase[4]);
    {
        System.out.print("character [b] located at position [1] is uppercase"); 
    }
}

As you can see, I couldn’t even figure out how to use the loop to print ‘a’ or ‘b’ and so I had to manually insert each one along with the position they’re in…

Answer 1

If you’re comparing two Strings (ie the arrays are String[]) then your code is comparing the memory reference of each string, which will be different.

In order to compare String for equality, you need to use the equals method.

for(x = 0; x < fullName.length(); x++)
{
    if(fullName[0].equals(nameUpperCase[2]));
    {
        System.out.print("character [0] located at position [0] is  lowercase");
    }

    if(fullName[1].equals(nameLowerCase[4]));
    {
        System.out.print("character [b] located at position [1] is uppercase"); 
    }

}

I would also recommend you take some of the ideas from the other answers.

Convert the original String to a char array instead…

char[] fullName = name.toCharArray();

Or you could simply get the char at the given index…

for(x = 0; x < originalString.length(); x++)
{
    char charAt = originalString.charAt(x);
    if(Character.isUpperCase(charAt));
    {
        System.out.print("character [0] located at position [0] is  lowercase");
    }

    if(Character.toUpperCase(originalString.charAt(1)) == originalString.charAt(4));
    {
        System.out.print("character [b] located at position [1] is uppercase"); 
    }

}

Updated example

Now that we’ve established that we can’t compare String values with ==, here’s a working example of what I think you want achieve…

String value = "This is a simple string";
for (int index = 0; index < value.length(); index++) {

    String whatIs = "Unknown";
    if (Character.isUpperCase(value.charAt(index))) {
        whatIs = "Upper case";
    } else if (Character.isLowerCase(value.charAt(index))) {
        whatIs = "Lower case";
    } else if (Character.isSpaceChar(value.charAt(index))) {
        whatIs = "Space";
    } else if (Character.isDigit(value.charAt(index))) {
        whatIs = "Digit";
    }

    System.out.println("Character @ " + index + " (" + value.charAt(index) + ") is a " + whatIs + " character");

}

Which outputs

Character @ 0 (T) is a Upper case character
Character @ 1 (h) is a Lower case character
Character @ 2 (i) is a Lower case character
Character @ 3 (s) is a Lower case character
Character @ 4 ( ) is a Space character
Character @ 5 (i) is a Lower case character
Character @ 6 (s) is a Lower case character
Character @ 7 ( ) is a Space character
Character @ 8 (a) is a Lower case character
Character @ 9 ( ) is a Space character
Character @ 10 (s) is a Lower case character
Character @ 11 (i) is a Lower case character
Character @ 12 (m) is a Lower case character
Character @ 13 (p) is a Lower case character
Character @ 14 (l) is a Lower case character
Character @ 15 (e) is a Lower case character
Character @ 16 ( ) is a Space character
Character @ 17 (s) is a Lower case character
Character @ 18 (t) is a Lower case character
Character @ 19 (r) is a Lower case character
Character @ 20 (i) is a Lower case character
Character @ 21 (n) is a Lower case character
Character @ 22 (g) is a Lower case character