CODEWITHSUNDEEP
java
Swanand Pangam
Swanand Pangam

Reputation: 898

Unknown output by System.out.println

I am learning Java and while studying try catch loop, I encountered this weird behaviour.

Whatever number I supply to the below code, it returns something between 49 - 53.

public class demo{
    public static void main(String[] args) {
        System.out.println("Enter a number");
        try{
            int num = System.in.read();
            System.out.println(num);
        }catch(Exception e){
            e.printStackTrace();
        }       
    }
}

Upvotes: 2

Views: 307

Answers (3)

MrProper
MrProper

Reputation: 1043

InputStream.read() reads only the next byte of data:

http://docs.oracle.com/javase/7/docs/api/java/io/InputStream.html#read()

If you'll need to read more than 1 byte of data at a time, try using a BufferedInputStream: http://docs.oracle.com/javase/7/docs/api/java/io/BufferedInputStream.html or a reader: https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html

Beware of simply casting an int produced by InputStream.read to char - it will only work if your character set is ISO-8859-1. Hence, a Reader with appropriate Charset is a good option.

Upvotes: 0

rgettman
rgettman

Reputation: 178243

You must have entered numbers 1-5. The read() method of InputStream (System.in is an InputStream) returns the byte value as an int, but the value is the Unicode code. The characters '1' through '5' are represented by the codes 49-53. In fact, '0' through '9' are represented by the codes 48-57.

Don't call read directly on the InputStream. It's meant for low-level stream processing. Instead, wrap the InputStream in a Scanner and call nextInt().

Upvotes: 7

ControlAltDel
ControlAltDel

Reputation: 35011

InputStream.read() returns an integer. You should do char c = (char) myInt; to convert it to a character if that's what you want

Upvotes: 1

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