error: incompatible types: char cannot be converted to String - Java

Question

This is just a part of my code that I have problem troubleshooting.

static int checkConcat(String number) {
        TreeSet<Integer> a = new TreeSet<Integer>();
        for(int i=0; i<number.length(); i++) {
            a.add(Integer.parseInt(number.charAt(i)));
        }
}

The error that I'm getting is :

error: incompatible types: char cannot be converted to String

What's wrong with the code, and how can I solve it in this context?

You asked a (simple) question, and you've got several answers. So, why didn't you accepted one of them? It seems to me that in these answers is a at least one solution for you. — zlakad, Jan 26 '18 at 13:22
@Dukeling, I didn't mean to be rude, but for **this** kind of question and these answers? — zlakad, Jan 26 '18 at 13:34

score 6 · Accepted Answer · answered Jan 26 '18 at 13:16

6

You can easily convert the char to String.

char aCharacter = 'c';
String aCharacterAsString = String.valueOf(aCharacter);

So in your case:

a.add(Integer.parseInt(String.valueOf(number.charAt(i))));

answered Jan 26 '18 at 13:16

George Z.

6,643
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score 3 · Answer 2 · 2018-01-26T13:23:18.943

3

Integer.parseInt(String s) has the argument type String, not char as returned by number.charAt(i).

Convert to a String:

a.add(Integer.parseInt("" + number.charAt(i)));

edited Jan 26 '18 at 13:23

answered Jan 26 '18 at 13:13

Can you rewrite the solution to solve the above problem using my code? – Jan 26 '18 at 13:16
1

Of course I can, but why don't you try it yourself? – Jan 26 '18 at 13:23

score 0 · Answer 3 · answered Jan 26 '18 at 13:13

A single character is char, not String. Although you could construct a single-character string from char using a method described below, parsing a number digit-by-digit should be done with a different API:

for(int i=0; i<number.length(); i++) {
    a.add(Character.digit(number.charAt(i), 10));
}

To construct a single-character string from char in Java, use String.valueOf method:

String singleDigit = String.valueOf(number.charAt(i));

score 0 · Answer 4 · answered Jan 26 '18 at 13:17

0

charAt returns one character of the string, therefore the return type is char not string to convert to string use the String.valueOf method:

String.valueOf(number.charAt(i))

Or don't use Integer.parse just subtract '0' from the character to convert it to the digit value. This would be a simpler more efficient way to convert a single digit value.

number.charAt(i) -'0'

answered Jan 26 '18 at 13:17

Titian Cernicova-Dragomir

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The trick of subtracting zero character, borrowed from C, was foreign to Java since day one, because Java standard library has `Character.digit` method. To be honest, I was unaware of its existence for many years, diligently writing `ch-'0'` in my Java code. – Sergey Kalinichenko Jan 26 '18 at 13:24

error: incompatible types: char cannot be converted to String - Java

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