System.in.read() is misbehaving when trying to enter integer value

Question

I'm trying to enter integer value through System.in.read(). But when I'm reading the value it is giving different output 49 for 1, 50 for 2 & so on int e=(int)System.in.read(); System.out.print("\n"+e);

The reason for that is that the `System.in.read()` reads a character, not an integer. So when you cast the char '1' to an int, you get the ASCII value of the char '1', which is 49. — Dimitar Spasovski, Jun 10 '18 at 21:03

Oleg Cherednik · Answer 1 · 2018-06-10T21:52:26.833

2

Because character 1 (i.e. char ch = '1') has ASCII code 49 (i.e. int code = '1' is 49).

System.out.println((int)'1'); // 49

To fix your examle, just substract code for 0:

int e = System.in.read() - '0';
System.out.println(e); // 1

edited Jun 10 '18 at 21:52

answered Jun 10 '18 at 21:02

Oleg Cherednik

17,377
4
21
35

Better yet, don't use `read()`. – Andreas Jun 10 '18 at 21:20
1

@Andreas I agree, `Scanner` is much better, but this is not a scope of this question. – Oleg Cherednik Jun 10 '18 at 21:40

namokarm · Answer 2 · 2018-06-10T21:27:26.640

1

You're reading char with function

System.in.read()

You can see the use of System.in.read() here. Also please check here how to read a value from user.

edited Jun 10 '18 at 21:27

answered Jun 10 '18 at 21:05

namokarm

668
1
7
20

1

No *"cast to int"*, since [`read()`](https://docs.oracle.com/javase/8/docs/api/java/io/InputStream.html#read--) returns an `int`. – Andreas Jun 10 '18 at 21:19
Thanks for the link and the correction @Andreas. – namokarm Jun 10 '18 at 21:28

Kröw · Answer 3 · 2018-06-10T21:48:40.183

As other answers have mentioned, System.in.read() reads in a single character in the form of an int, or -1 if there is no input to read in. This means that characters read in with System.in.read() will be ints representing ASCII values of the read characters.

To read in an integer from System.in it might be easier to use a Scanner:

Scanner s = new Scanner(System.in);
int e = s.nextInt();
System.out.print("\n"+e);
s.close();

or, if you wish to stick to using System.in.read(), you can use Integer.parseInt(String) to obtain an integer off of the character input from System.in.read():

int e = Integer.parseInt("" + (char) System.in.read());
System.out.print("\n"+e);

Integer.parseInt(String) will throw a NumberFormatException you can catch if the input is not a number.

System.in.read() is misbehaving when trying to enter integer value

3 Answers3