What does :
System.in.read()
return ? The documentation says :
Returns: the next byte of data, or -1 if the end of the stream is reached.
But for example if I enter : 10
I get back 49
. Why is that ?
System indicates the current computer system. System. in. read indicates reading from a standard input device.
System.in: An InputStream which is typically connected to keyboard input of console programs. It is nothing but an in stream of OS linked to System class. Using System class, we can divert the in stream going from Keyboard to CPU into our program. This is how keyboard reading is achieved in Java.
49
is the ASCII value of the char 1
. It is the value of the first byte.
The stream of bytes that is produced when you enter 10Enter on your console or terminal contains the three bytes {49,48,10}
(on my Mac, may end with 10,12 or 12 instead of 10, depending on your System).
So the output of the simple snippet
int b = System.in.read();
while (b != -1) {
System.out.println(b);
b = System.in.read();
}
after entering a 10 and hitting enter, is (on my machine)
49
48
10
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