在System.in.read（）之后，扫描仪nextLine（）不起作用

Question

I have following code and am facing a problem if I use System.in.read() before Scanner .
Then the cursor moves at the end by skipping nextLine() function.

import java.util.Scanner;
public class InvoiceTest{
public static void main(String [] args) throws java.io.IOException {
    System.out.println("Enter a Charater: ");
    char c = (char) System.in.read();

    Scanner input = new Scanner(System.in);
    System.out.println("Enter id No...");
    String id_no = input.nextLine();

    System.out.println("Charater You entered "+ c +" Id No Entered "+ id_no);

    }
}

Answer 1

You are not consuming the newline character upon entering your character( System.in.read() ) thus the input.nextLine() will consume it and skip it.

solution:

consume the new line character first before reading the input of for the id.

System.out.println("Enter a Charater: ");
    char c = (char) System.in.read();

    Scanner input = new Scanner(System.in);
    System.out.println("Enter id No...");
    input.nextLine(); //will consume the new line character spit by System.in.read()
    String id_no = input.nextLine();

    System.out.println("Charater You entered "+c+" Id No Entered "+id_no);

    }

Answer 2

EJP comments thus:

Don't mix System.in.read() with new Scanner(System.in). Use one or the other.

Good advice!

So why is it a bad idea to mix reading from the stream and using Scanner ?

Well, because Scanner operations will typically read ahead on the input stream, keeping unconsumed characters in an internal buffer. So if you do a Scanner operation followed by a call to read() on the stream, there is a good chance that the read() will (in effect) skip over characters. The behaviour is likely to be confusing and unpredictable ... and dependent on where the input characters are actually coming from.