File in Java how to Read and Write File in Java

You can use class in package java.io.* to manage file with java
for example below

Example code for read file line by line with Java

  FileInputStream fs = new FileInputStream("filename.txt"); 
  DataInputStream ds = new DataInputStream(fs);
  BufferedReader br = new BufferedReader(new InputStreamReader(ds));
  String tmp; 
  while ((tmp = br.readLine()) != null)   {
      System.out.println (tmp);
  } 
  ds.close();

Example code for Write file with java
  FileWriter fw = new FileWriter("file_name.txt");
  BufferedWriter out = new BufferedWriter(fw);
  out.write("Test Wrrite1");
  out.write("Test Wrrite2");
  out.write("Test Wrrite3");  
  out.close();

Java Class is based for Java OOP

Class is the blueprint to create Object  Class is learning the basics of OOP that everyone must know.

for example

Object of  Class Car is  My car .

Class structure

prefix eg.(public,protected) class ClassName {
  
}

public class MyClass{
 //implement some things
}