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Java Exercises: Read a plain text file

Java Input-Output: Exercise-12 with Solution

Write a Java program to read a plain text file.

Sample Solution:

Java Code:

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.FileInputStream;
import java.io.FileReader;
 
public class Exercise12 {
 
    public static void main(String a[]){
        StringBuilder sb = new StringBuilder();
        String strLine = "";
        try {
             BufferedReader br = new BufferedReader(new FileReader("/home/students/test.txt"));
             while (strLine != null)
             {
                sb.append(strLine);
                sb.append(System.lineSeparator());
                strLine = br.readLine();
                System.out.println(strLine);
            }
             br.close();
        } catch (FileNotFoundException e) {
            System.err.println("File not found");
        } catch (IOException e) {
            System.err.println("Unable to read the file.");
        }
     }
}

Sample Output:

Welcome to w3resource.com.                                                                                    
Append this text.Append this text.Append this text.                                                           
Append this text.                                                                                             
Append this text.                                                                                             
Append this text.                                                                                             
Append this text.                                                                                             
null 

Flowchart:

Flowchart: Read a plain text file

Java Code Editor:

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Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH