Take a char input from the Scanner

Question

I am trying to find a way to take a char input from the keyboard.

I tried using:

Scanner reader = new Scanner(System.in);
char c = reader.nextChar();

This method doesn't exist.

I tried taking c as a String. Yet, it would not always work in every case, since the other method I am calling from my method requires a char as an input. Therefore I have to find a way to explicitly take a char as an input.

Any help?

Reimeus · Accepted Answer · 2014-04-15T20:58:51.263

172

You could take the first character from Scanner.next:

char c = reader.next().charAt(0);

To consume exactly one character you could use:

char c = reader.findInLine(".").charAt(0);

To consume strictly one character you could use:

char c = reader.next(".").charAt(0);

edited Apr 15 '14 at 20:58

answered Dec 18 '12 at 22:43

Reimeus

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See http://stackoverflow.com/questions/4007534/why-cant-we-read-one-character-at-a-time-from-system-in – Reimeus Dec 18 '12 at 23:36
7

Actually its taking more than one character, but acting only on the first character – Ralph Dec 19 '12 at 02:39
I want to provide my program with a character and the program should only accept characters ! – Ralph Dec 19 '12 at 02:39
2

@user1804697 to consume just characters use `char c = reader.next("[a-zA-Z]").charAt(0);` – Reimeus Apr 15 '14 at 21:10
@UnKnown findInLine(regex) search buffered line for givin regex if found return that string and increment position else return null. – Error Jun 25 '16 at 22:36
14

What's the difference between "exactly" and "strictly" in this context? – Nov 29 '17 at 18:02
2

@Reimeus what exactly is the value in copy pasting code and then running it? – bharal Jun 07 '18 at 17:37
@tilper Try and enter more than 1 character in each case and you will discover the difference :) – Reimeus Jan 04 '19 at 11:23
2

Well, the `next()` version crashes on the gibberish input `bhjgfbergq35987t%$#%$#` and the `findInLine()` version doesn't. My question was really more about the words "strictly" and "exactly" and not the corresponding code fragments. I'm unaware of a context in which those words are not synonyms. – Jan 04 '19 at 13:50

score 57 · Answer 2 · answered Jan 18 '15 at 08:42

57

Setup scanner:

reader.useDelimiter("");

After this reader.next() will return a single-character string.

answered Jan 18 '15 at 08:42

hoat4

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score 18 · Answer 3 · edited Apr 06 '15 at 00:51

18

There is no API method to get a character from the Scanner. You should get the String using scanner.next() and invoke String.charAt(0) method on the returned String.

Scanner reader = new Scanner(System.in);
char c = reader.next().charAt(0);

Just to be safe with whitespaces you could also first call trim() on the string to remove any whitespaces.

Scanner reader = new Scanner(System.in);
char c = reader.next().trim().charAt(0);

edited Apr 06 '15 at 00:51

Radiodef

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answered Dec 18 '12 at 22:43

PermGenError

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Wouldn't `reader.next()` already give you the string starting from the first non-white char? – norok2 Jun 25 '20 at 10:07
but this consumes entire string. – Rainning Dec 20 '20 at 05:12

Stephen C · Answer 4 · 2018-01-13T00:02:53.517

There are three ways to approach this problem:

Call next() on the Scanner, and extract the first character of the String (e.g. charAt(0)) If you want to read the rest of the line as characters, iterate over the remaining characters in the String. Other answers have this code.
Use setDelimiter("") to set the delimiter to an empty string. This will cause next() to tokenize into strings that are exactly one character long. So then you can repeatedly call next().charAt(0) to iterate the characters. You can then set the delimiter to its original value and resume scanning in the normal way!

Use the Reader API instead of the Scanner API. The Reader.read() method delivers a single character read from the input stream. For example:

Reader reader = new InputStreamReader(System.in);
int ch = reader.read();
if (ch != -1) {  // check for EOF
    // we have a character ...
}

When you read from the console via System.in, the input is typically buffered by the operating system, and only "released" to the application when the user types ENTER. So if you intend your application to respond to individual keyboard strokes, this is not going to work. You would need to do some OS-specific native code stuff to turn off or work around line-buffering for console at the OS level.

Reference:

How to read a single char from the console in Java (as the user types it)?

"This will cause next() to tokenize into strings that are exactly one character long. So then you can repeatedly call __next().charAt(0)__ to iterate the characters." I think you meant `next()` only since you already `setDelimiter("")`? But +1 for your third point. — Rainning, Dec 20 '20 at 05:20
No, I did really mean `next().charAt(0)`. The `next` call returns a `String`. So if you want to iterate the `char` values, you need to call `charAt(0)` to get the first character. (This is Java where a character and a one character string are not the same thing.) Note that the OP **explicitly** states that a `char` is required. — Stephen C, Dec 20 '20 at 05:30

score 5 · Answer 5 · answered Nov 17 '18 at 22:54

You can solve this problem, of "grabbing keyboard input one char at a time" very simply. Without having to use a Scanner all and also not clearing the input buffer as a side effect, by using this.

char c = (char)System.in.read();

If all you need is the same functionality as the C language "getChar()" function then this will work great. The Big advantage of the "System.in.read()" is the buffer is not cleared out after each char your grab. So if you still need all the users input you can still get the rest of it from the input buffer. The "char c = scanner.next().charAt(0);" way does grab the char but will clear the buffer.

// Java program to read character without using Scanner
public class Main
{
    public static void main(String[] args)
    {
        try {
            String input = "";
            // Grab the First char, also wait for user input if the buffer is empty.
            // Think of it as working just like getChar() does in C.
            char c = (char)System.in.read();
            while(c != '\n') {
                //<do your magic you need to do with the char here>
                input += c; // <my simple magic>

                //then grab the next char
                c = (char)System.in.read();
            }
            //print back out all the users input
            System.out.println(input);
        } catch (Exception e){
            System.out.println(e);
        }
    }
}

Hope this helpful, and good luck! P.S. Sorry i know this is an older post, but i hope that my answer bring new insight and could might help other people who also have this problem.

score 4 · Answer 6 · edited May 23 '17 at 12:18

This actually doesn't work:

char c = reader.next().charAt(0);

There are some good explanations and references in this question: Why doesn't the Scanner class have a nextChar method? "A Scanner breaks its input into tokens using a delimiter pattern", which is pretty open ended. For example when using this

c = lineScanner.next().charAt(0);

for this line of input "(1 + 9) / (3 - 1) + 6 - 2" the call to next returns "(1", c will be set to '(', and you'll end up losing the '1' on the next call to next()

Typically when you want to get a character you would like to ignore whitespace. This worked for me:

c = lineScanner.findInLine("[^\\s]").charAt(0);

Reference: regex to match a single character that is anything but a space

1

FYI `"[^\\s]" === "\\S"` – Bohemian Jul 27 '15 at 16:30

score 1 · Answer 7 · edited Jan 14 '14 at 16:37

1

The best way to take input of a character in Scanner class is:

Scanner sca=new Scanner(System.in);
System.out.println("enter a character");
char ch=sca.next().charAt(0);

edited Jan 14 '14 at 16:37

Ben

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answered Jan 14 '14 at 16:19

Sahil Gupta

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NIKUNJ KHOKHAR · Answer 8 · 2017-06-16T06:23:40.773

1

You should use your custom input reader for faster results instead of extracting first character from reading String. Link for Custom ScanReader and explanation: https://gist.github.com/nik1010/5a90fa43399c539bb817069a14c3c5a8

Code for scanning Char :

BufferedInputStream br=new BufferedInputStream(System.in);
char a= (char)br.read();

edited Jun 16 '17 at 06:23

answered Jun 16 '17 at 05:59

NIKUNJ KHOKHAR

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You should add the code from the gist in your answer as it might be inavailable some time. – Markus Jun 16 '17 at 06:20
@Markus added for scanning char. – NIKUNJ KHOKHAR Jun 16 '17 at 06:24

score 1 · Answer 9 · edited Dec 20 '20 at 05:36

1

import java.util.Scanner;

public class Test { 
    public static void main(String[] args) {
 
        Scanner reader = new Scanner(System.in);
        char c = reader.next(".").charAt(0);

    }
}

To get only one character char c = reader.next(".").charAt(0);

edited Dec 20 '20 at 05:36

Stephen C

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answered Oct 16 '17 at 13:51

Rakesh Kumar B

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To get only one character char c = reader.next(".").charAt(0); – Rakesh Kumar B Oct 16 '17 at 13:52

score 1 · Answer 10 · answered Apr 24 '19 at 06:19

There are two approaches, you can either take exactly one character or strictly one character. When you use exactly, the reader will take only the first character, irrespective of how many characters you input.

For example:

import java.util.Scanner;  

public class ReaderExample {  

    public static void main(String[] args) {  

        try {  

        Scanner reader = new Scanner(System.in);

        char c = reader.findInLine(".").charAt(0);

            reader.close();  

            System.out.print(c);

        } catch (Exception ex) {  

            System.out.println(ex.getMessage());  

        }



    }  

}

When you give a set of characters as input, say "abcd", the reader will consider only the first character i.e., the letter 'a'

But when you use strictly, the input should be just one character. If the input is more than one character, then the reader will not take the input

import java.util.Scanner;  

public class ReaderExample {  

    public static void main(String[] args) {  

        try {  

        Scanner reader = new Scanner(System.in);

        char c = reader.next(".").charAt(0);

            reader.close();  

            System.out.print(c);

        } catch (Exception ex) {  

            System.out.println(ex.getMessage());  

        }



    }  

}

Suppose you give input "abcd", no input is taken, and the variable c will have Null value.

score 0 · Answer 11 · answered Feb 15 '15 at 14:24

import java.util.Scanner;

public class userInput{
    public static void main(String[] args){
        // Creating your scanner with name kb as for keyBoard
        Scanner kb = new Scanner(System.in);

        String name;
        int age;
        char bloodGroup;
        float height;

        // Accepting Inputs from user
        System.out.println("Enter Your Name");
        name = kb.nextLine(); // for entire line of String including spaces
        System.out.println("Enter Your Age");
        age = kb.nextInt(); // for taking Int
        System.out.println("Enter Your BloodGroup : A/B/O only");
        bloodGroup  = kb.next().charAt(0); // For character at position 0
        System.out.println("Enter Your Height in Meters");
        height = kb.nextFloat(); // for taking Float value

        // closing your scanner object
        kb.close();

        // Outputting All
        System.out.println("Name : " +name);
        System.out.println("Age : " +age);
        System.out.println("BloodGroup : " +bloodGroup);
        System.out.println("Height : " +height+" m");

    }
}

score 0 · Answer 12 · answered Sep 14 '16 at 14:28

0

Try this: char c=S.nextLine().charAt(0);

answered Sep 14 '16 at 14:28

Harshal Mande

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1

Abdo Bmz · Answer 13 · 2018-04-19T19:58:50.593

You should get the String using scanner.next() and invoke String.charAt(0) method on the returned String.
Exmple :

    import java.util.Scanner;

    public class InputC{


            public static void main(String[] args) {
                // TODO Auto-generated method stub
                   // Declare the object and initialize with
                   // predefined standard input object
                    Scanner scanner = new Scanner(System.in);
                    System.out.println("Enter a character: ");
                    // Character input
                    char c = scanner.next().charAt(0);
                    // Print the read value
                    System.out.println("You have entered: "+c);
            }


        }

output

Enter a character: 
a
You have entered: a

score 0 · Answer 14 · answered Jan 31 '20 at 18:51

0

you just need to write this for getting value in char type.

char c = reader.next().charAt(0);

answered Jan 31 '20 at 18:51

bilal Tashfeen

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score 0 · Answer 15 · answered Jan 29 '21 at 05:58

0

Simple solution to read a charachter from user input. Read a String. Then use charAt(0) over String

Scanner reader = new Scanner(System.in);
String str = reader.next();
char c = str.charAt(0);

That's it.

answered Jan 29 '21 at 05:58

Steve

21
4

score -1 · Answer 16 · edited Jun 27 '20 at 17:12

-1

Just use...

Scanner keyboard = new Scanner(System.in);
char c = keyboard.next().charAt(0);

This gets the first character of the next input.

edited Jun 27 '20 at 17:12

Yolomep

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answered Dec 15 '16 at 03:05

Razoowp

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score -1 · Answer 17 · answered Apr 19 '18 at 17:32

-1

// Use a BufferedReader to read characters from the console.
import java.io.*;
class BRRead {
public static void main(String args[]) throws IOException
{
char c;
BufferedReader br = new
BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter characters, 'q' to quit.");
// read characters
do {
c = (char) br.read();
System.out.println(c);
} while(c != 'q');
}
}

answered Apr 19 '18 at 17:32

John Born

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What's the difference between `InputStreamReader` and `BufferedReader`? You used that in your code but you didn't explain. – Rainning Dec 20 '20 at 05:22

score -2 · Answer 18 · edited Apr 06 '15 at 21:55

-2

import java.io.*;

class abc // enter class name (here abc is class name)
{
    public static void main(String arg[])
    throws IOException // can also use Exception
    {
        BufferedReader z =
            new BufferedReader(new InputStreamReader(System.in));

        char ch = (char) z.read();
    } // PSVM
} // class

edited Apr 06 '15 at 21:55

Radiodef

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answered Dec 22 '14 at 09:50

vishu

1

score -2 · Answer 19 · answered Aug 17 '16 at 20:30

-2

Try this

Scanner scanner=new Scanner(System.in);
String s=scanner.next();
char c=s.charAt(0);

answered Aug 17 '16 at 20:30

Farhan

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but this consumes entire string, you return. – Rainning Dec 20 '20 at 05:13

score -2 · Answer 20 · answered Nov 23 '16 at 02:52

Scanner key = new Scanner(System.in);
//shortcut way 
char firstChar=key.next().charAt(0);  
//how it works;
/*key.next() takes a String as input then,
charAt method is applied on that input (String)
with a parameter of type int (position) that you give to get      
that char at that position.
You can simply read it out as: 
the char at position/index 0 from the input String
(through the Scanner object key) is stored in var. firstChar (type char) */

//you can also do it in a bit elabortive manner to understand how it exactly works
String input=key.next();  // you can also write key.nextLine to take a String with spaces also
char firstChar=input.charAt(0);
char charAtAnyPos= input.charAt(pos);  // in pos you enter that index from where you want to get the char from

By the way, you can't take a char directly as an input. As you can see above, a String is first taken then the charAt(0); is found and stored

score -3 · Answer 21 · edited Mar 26 '16 at 20:35

-3

You could use typecasting:

Scanner sc= new Scanner(System.in);
char a=(char) sc.next();

This way you will take input in String due to the function 'next()' but then it will be converted into character due to the 'char' mentioned in the brackets.

This method of conversion of data type by mentioning the destination data type in brackets is called typecating. It works for me, I hope it works for u :)

edited Mar 26 '16 at 20:35

aribeiro

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answered Mar 26 '16 at 20:15

Nihaarika

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You can't typecast a `String` to a `char`. – Stephen C Jan 12 '18 at 23:59

score -4 · Answer 22 · edited Jun 11 '16 at 00:39

To find the index of a character in a given sting, you can use this code:

package stringmethodindexof;

import java.util.Scanner;
import javax.swing.JOptionPane;

/**
 *
 * @author ASUS//VERY VERY IMPORTANT
 */
public class StringMethodIndexOf {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        String email;
        String any;
        //char any;

//any=JOptionPane.showInputDialog(null,"Enter any character or string to find out its INDEX NUMBER").charAt(0);       
//THE AVOBE LINE IS FOR CHARACTER INPUT LOL
//System.out.println("Enter any character or string to find out its INDEX NUMBER");
       //Scanner r=new Scanner(System.in);
      // any=r.nextChar();
        email = JOptionPane.showInputDialog(null,"Enter any string or anything you want:");
         any=JOptionPane.showInputDialog(null,"Enter any character or string to find out its INDEX NUMBER");
        int result;
        result=email.indexOf(any);
        JOptionPane.showMessageDialog(null, result);

    }

}

score -8 · Answer 23 · edited Jan 18 '17 at 16:42

The easiest way is, first change the variable to a String and accept the input as a string. Then you can control based on the input variable with an if-else or switch statement as follows.

Scanner reader = new Scanner(System.in);

String c = reader.nextLine();
switch (c) {
    case "a":
        <your code here>
        break;
    case "b":
        <your code here>
        break;
    default: 
        <your code here>
}

Take a char input from the Scanner

23 Answers23

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