How come readLine() is not blocking?

Question

Given the following code, the first call to readLine() is not blocking, both "Enter name:" and "Enter address:" are printed at the same time, and address gets assigned to whatever is entered. Why? I've tried putting them in separate try blocks, getting rid of the loop and generally reordering things.

public class AddressReader {

public static void main(String[] args) {

    Path file = Paths.get("d:/java IO/addresses.txt");

    try {
        Files.createDirectories(file.getParent());
    } catch (IOException e) {
        System.err.println("Error craeting directory: " + file.getParent());
        e.printStackTrace();
        System.exit(1);
    }
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    int c = 0;
    try {
        System.out.println("<a>dd an entry or <r>ead entries");
        c = br.read();
    } catch (IOException e) {
        System.out.println("An error has occured, try again");
    }
    switch (c) {
    case 'a':
        String name = null;
        String address = null;

        while (name == null || name == "" || address == null || address == "") {
            try {
                System.out.println("Enter name:");
                name = br.readLine();
                System.out.println("Enter address:");
                address = br.readLine();
            } catch (IOException e) {
                System.out.println("An error has occured, try again");
            }
            System.out.println("name = " + name);
            System.out.println("address = " + address);
        }
        //writeEntry(file, name, address);
        break;
    case 'r':
        //readEntries(file);
        break;
    default:
        System.out.println("Invalid entry, try again.");
    }

}

}

your string equality check is wrong. you should use equals() method, not == operator — PermGenError, Feb 17 '13 at 22:13
See also: http://stackoverflow.com/questions/2772763 and http://stackoverflow.com/questions/513832 — Tomasz Nurkiewicz, Feb 17 '13 at 22:14
you're right about the string check, but thats not whats causing the problem — Steve M, Feb 17 '13 at 22:15

score 3 · Accepted Answer · answered Feb 17 '13 at 22:24

3

This is because of this line:

c = br.read();

This does not consume the new-line character that is produced by pressing ENTER.

To solve this issue, use this instead:

c = br.readLine().charAt(0);

answered Feb 17 '13 at 22:24

Eng.Fouad

115,165
71
313
417

score 0 · Answer 2 · answered Feb 17 '13 at 22:18

Over and above whats already been said, for what you're trying to do I suggest using the Console instead:

Console console = System.console();
String name = console.readLine("Create a name.");
char[] password = console.readPassword("Create a password.");
System.out.println(name + ":" + new String(password));

How come readLine() is not blocking?

2 Answers2