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Java Exercises: Append text to an existing file

Java Input-Output: Exercise-16 with Solution

Write a Java program to append text to an existing 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;
import java.io.FileWriter;
 
public class Exercise16 {
     public static void main(String a[]){
        StringBuilder sb = new StringBuilder();
        String strLine = "";
        try
          {
             String filename= "/home/students/myfile.txt";
             FileWriter fw = new FileWriter(filename,true); 
             //appends the string to the file
             fw.write("Java Exercises\n");
             fw.close();
             BufferedReader br = new BufferedReader(new FileReader("/home/students/myfile.txt"));
             //read the file content
             while (strLine != null)
             {
                sb.append(strLine);
                sb.append(System.lineSeparator());
                strLine = br.readLine();
                System.out.println(strLine);
            }
             br.close();
           }
           catch(IOException ioe)
           {
            System.err.println("IOException: " + ioe.getMessage());
           }
        }
  }

Sample Output:

Python Exercises                                                                                              
Java Exercises                                                                                                
null

Flowchart:

Flowchart: Append text to an existing file

Java Code Editor:

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Next: Write a Java program to read first 3 lines from a file.

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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