为什么.size（）在此ArrayList上无法正常工作？

Question

I've imported a dat file into an ArrayList. My issue is that, although it prints out all the names in the file, it won't give me the correct size. Instead, it just prints out 1.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

public class TestArray {
    public static void main (String [] args){
    String filePath = "C:\\Users\\Admin\\workspace\\Fund III\\src\\names.dat";

    Scanner sc = null;
    try {

        sc = new Scanner(new File (filePath ));
    } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    //Makes Array list
    ArrayList<String> nameList = new ArrayList<String>();

    //Dumps names into array
try{
    while(sc.hasNextLine())
    {
        nameList.add(sc.nextLine());
    }
   }
    catch(Exception e)
    {
        System.out.println("Error: " + e);
    }
    System.out.println(nameList.size());
    System.out.println(nameList);
}
}

Answer 1

It appears that your file has only one line. Here is how to check:

while(sc.hasNextLine()) {
    String line = sc.nextLine();
    nameList.add(line);
    System.out.println("Line: '"+line+"'");
}

Run your modified program, and watch for single quotes around your strings. If your output produces multiple lines inside a single pair of quotes, the issue is that your input does not have end-of-line markers expected by the system on which you run your program.

Answer 2

According to Scanner java doc ...

The default whitespace delimiter used by a scanner is as recognized by Character.isWhitespace .

Are you sure you understand the content of the file and how it has been created (Linux/Windows).

For example when running a Java process on Linux and reading a file that has been created on Windows, I often have to use the dos2unix command to correct the file format, otherwise it won't process as expected unless you put extra effort into specifying the correct file encoding in your java code.