从控制台读取多行并将其存储在Java的数组列表中？

Question

Can anyone please help me with the code as how to read multiple lines from console and store it in array list? Example, my input from the console is:

12     abc      place1
13     xyz      place2

and I need this data in ArrayList.

So far I tried this code:

Scanner scanner = new Scanner(System.in);
ArrayList informationList = new ArrayList<ArrayList>();
String information = "";
int blockSize = 0, count = 1;
System.out.println("Enter block size");
blockSize = scanner.nextInt();
System.out.println("Enter the Information ");
while (scanner.hasNext() && blockSize >= count) {
    scanner.useDelimiter("\t");
    information = scanner.nextLine();
    informationList.add(information);
    count++;
}

Any help is greatly appreciated.

Input line from console is mix of string and integer

Answer 1

You've got a few problems.

First of all, the initialization line for your ArrayList is wrong. If you want a list of Object so you can hold both Integers and Strings, you need to put Object inside the angle braces. Also, you're best off adding the generic type argument to the variable definition instead of just on the object instantiation.

Next, your count is getting messed up because you're initializing it to 1 instead of 0. I'm assuming "block size" really means the number of rows here. If that's wrong leave a comment.

Next, you don't want to reset the delimiter your Scanner is using, and you certainly don't want to do it inside your loop. By default a Scanner will break up tokens based on any whitespace which I think is what you want since your data is delimited both by tabs and newlines.

Also, you don't need to check hasNext() in your while condition. All of the next*() methods will block waiting for input so the call to hasNext() is unnecessary.

Finally, you're not really leveraging the Scanner to do what it does best which is parse tokens into whatever type you want. I'm assuming here that every data line is going to start with a single integer and the be followed by two strings. If that's the case, just make a call to nextInt() followed by two calls to next() inside your loop and you'll get all the data parsed out into the data types you need automatically.

To summarize, here is your code updated with all my suggestions as well as some other bits to get it to run:

import java.util.ArrayList;
import java.util.Scanner;

public class Example {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        ArrayList<Object> list = new ArrayList<>();
        System.out.println("Enter block size");
        int blockSize = scanner.nextInt();
        System.out.println("Enter data rows:");
        int count = 0;
        while (count < blockSize) {
            list.add(scanner.nextInt());
            list.add(scanner.next());
            list.add(scanner.next());
            count++;
        }
        System.out.println("\nThe data you entered is:");
        System.out.println(list);
    }
}