How to capture enter key, using scanner as console input?

问题

I want to capture enter character in console. I am inputting 2 strings.

Case 1. removestudent(pressing enter) removes all the students from array list.

Case 2. removestudent student1 removes students1 from array list.

Scanner in=new Scanner();

type_op=in.next();

param=in.next();

if (type_op.equals("removestudent"))
{

    //Calling remove student function and passing param over here.

}

Now the case 2 works fine. However, for Case 1, I want param value to be null when user presses enter. I will then pass param as a null value to my remove function and delete all the students in the array list.

list1.clear();

Please help me in knowing how to get this enter key.

回答1:

You can read line and if line is blank, You can assume it is enter key.. like below code..

Scanner scanner = new Scanner(System.in);
String readString = scanner.nextLine();
System.out.println(readString);
if (readString.equals(""))
    System.out.println("Enter Key pressed.");
if (scanner.hasNextLine())
    readString = scanner.nextLine();
else
    readString = null;

回答2:

I think this will help you

Scanner input= new Scanner(System.in);
String readString = input.nextLine();
while(readString!=null) {
    System.out.println(readString);
    if (readString.equals(""))
        System.out.println("Read Enter Key.");
    if (input.hasNextLine())
        readString = input.nextLine();
    else
        readString = null;
}

来源：https://stackoverflow.com/questions/23194290/how-to-capture-enter-key-using-scanner-as-console-input