Check out example codes for "how to read and write to a file in java". It will help you in understanding the concepts better.

Code Example 1

package FileHandling;
 
 // Import the File class
import java.io.File;
 
// Import the IOException class to handle errors
import java.io.IOException; 
 
public class CreateFile {
public static void main(String[] args) {
try {
// Creating an object of a file
File myObj = new File("D:FileHandlingNewFilef1.txt"); 
if (myObj.createNewFile()) {
System.out.println("File created: " + myObj.getName());
} else {
System.out.println("File already exists.");
}
} catch (IOException e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}
}

Code Example 2

import java.io.FileWriter;   // Import the FileWriter class
import java.io.IOException;  // Import the IOException class to handle errors

public class WriteToFile {
  public static void main(String[] args) {
    try {
      FileWriter myWriter = new FileWriter("filename.txt");
      myWriter.write("Files in Java might be tricky, but it is fun enough!");
      myWriter.close();
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

Code Example 3

// Creating a text File using FileWriter 
import java.io.FileWriter; 
import java.io.IOException; 
class CreateFile 
{ 
    public static void main(String[] args) throws IOException 
    { 
        // Accept a string  
        String str = "File Handling in Java using "+ 
                " FileWriter and FileReader"; 
  
        // attach a file to FileWriter  
        FileWriter fw=new FileWriter("output.txt"); 
  
        // read character wise from string and write  
        // into FileWriter  
        for (int i = 0; i < str.length(); i++) 
            fw.write(str.charAt(i)); 
  
        System.out.println("Writing successful"); 
        //close the file  
        fw.close(); 
    } 
}

Learn ReactJs, React Native from akashmittal.com