When you read in the year month day hour minutes with something like nextInt() it leaves rest of the line in the parser/buffer (even if it is blank) so when you call nextLine() you are reading the rest of this first line.

I suggest you call scan.nextLine() before you print your next prompt to discard the rest of the line.

Thankful to help. This error occurs because the nextInt() and nextDouble() methods don't read the newline characters of your input.

You can easily fix this either by parsing int from nextLine(): Integer.parseInt(scan.nextLine()) or simply using the InputStreamReader class as:

//sample code for understanding

InputStreamReader in=new InputStreamReader(System.in);
BufferedReader read=new BufferedReader(in);
//taking input
System.out.print("Enter a number: ");
int val=Integer.parseInt(read.readLine());
System.out.println("Value entered: "+val);

A simple example to illustrate how java.util.Scanner works would be reading a single integer from System.in. It's really quite simple.

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

To retrieve a username I would probably use sc.nextLine().

System.out.println("Enter your username: ");
Scanner scanner = new Scanner(System.in);
String username = scanner.nextLine();
System.out.println("Your username is " + username);

You could also use next(String pattern) if you want more control over the input, or just validate the username variable.

You'll find more information on their implementation in the API Documentation for java.util.Scanner