Reading a File into an ArrayList in Java
When working with text data, it's often useful to store it in a data structure for easy manipulation and processing. In Java, an ArrayList is a commonly used collection for holding a list of objects, including strings. This article demonstrates how to read the contents of a file into an ArrayList of strings.
File Preparation
First, ensure you have a text file with line-separated data, as shown in the provided example:
cat house dog ...
Java Code to Read the File
To read the contents of the file into an ArrayList of strings, use the following code:
import java.util.ArrayList; import java.util.Scanner; import java.io.File; public class FileToList { public static void main(String[] args) { try { // Create a Scanner object for the file Scanner s = new Scanner(new File("filepath")); // Create an ArrayList to store the words ArrayList<string> list = new ArrayList(); // Loop through the file and add each word to the ArrayList while (s.hasNext()) { list.add(s.next()); } // Close the Scanner s.close(); // Print the ArrayList to the console System.out.println(list); } catch (Exception e) { e.printStackTrace(); } } }</string>
Explanation
- The code instantiates a Scanner object to read the file.
- It creates an empty ArrayList to store the strings.
- A while loop is used to iterate through each word in the file.
- The s.next() method retrieves the next word and adds it to the ArrayList.
- After reading the entire file, the Scanner is closed.
- The ArrayList is printed to the console for inspection.
Alternative for Reading Line by Line
If you prefer to read the file line by line instead of word by word, modify the code as follows:
... // Loop through the file and add each line to the ArrayList while (s.hasNextLine()) { list.add(s.nextLine()); } ...
In this case, s.hasNextLine() checks for the presence of a new line, and s.nextLine() retrieves the entire line.
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