Nextline和扫描程序是否忽略Java中的行？

Question

Scanner s = new Scanner (System.in);
while(!s.nextLine().isEmpty()){

a.add(i, s.nextLine());
i++;
}

System.out.println(a.size());

I created an Arraylist because I was copy and pasting an unknown amount of strings into the ide to be scanned, which may be an issue for the end of line.

I was testing out three lines by pasting them in. For example take the following example:

Hello
World
Again

I would copy and paste them in and the size of the Arraylist would be 2 and it would be World which would occupy at position 0.

My own theory is that he while loop takes the first line to check whether it is empty and then the second line is put into the Arraylist with the third being checked and a blank being put into the second position.

Then there is the pasting of the strings in the format of three lines and then pressing enter once which may affect the end of line. Does anyone have any insight into what is going on? Thanks,

Answer 1

You need to "capture" the line to be tested rather than throwing it away. Each call to s.nextLine() reads a line.

Scanner s = new Scanner (System.in);
String line;
while(!(line = s.nextLine()).isEmpty()){
    a.add(i, line);
    i++;
}

System.out.println(a.size());

Or as others have mentioned, you can use s.hasNext() as the loop condition as follows:

Scanner s = new Scanner (System.in);
while(s.hasNext()) {
    a.add(i, s.nextLine());
    i++;
}

System.out.println(a.size());