File I/O

java.io.File class to represent file object

import java.io.File;
 
public class FileClassDemo {
 
    public static void main(String[] args) {
        File f = new File("data/fruits.txt");
        System.out.println("full path: " + f.getAbsolutePath());
        System.out.println("file exists?: " + f.exists());
        System.out.println("is Directory?: " + f.isDirectory());
    }
 
}

java.util.Scanner can read a File object

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
 
public class FileReadingDemo {
 
    private static void printFileContents(String filePath) throws FileNotFoundException {
        File f = new File(filePath); // create a File for the given file path
        Scanner s = new Scanner(f); // create a Scanner using the File as the source
        while (s.hasNext()) {
            System.out.println(s.nextLine());
        }
    }
 
    public static void main(String[] args) {
        try {
            printFileContents("data/fruits.txt");
        } catch (FileNotFoundException e) {
            System.out.println("File not found");
        }
    }
 
}

↓i.e., contents of the data/fruits.txt

5 Apples
3 Bananas 
6 Cherries

java.io.FileWriter to write to a file

import java.io.FileWriter;
import java.io.IOException;
 
public class FileWritingDemo {
 
    private static void writeToFile(String filePath, String textToAdd) throws IOException {
        FileWriter fw = new FileWriter(filePath);
        // new FileWriter(filePath, true) for append mode
        fw.write(textToAdd);
        fw.close();
    }
 
    public static void main(String[] args) {
        String file2 = "temp/lines.txt";
        try {
            writeToFile(file2, "first line" + System.lineSeparator() + "second line");
        } catch (IOException e) {
            System.out.println("Something went wrong: " + e.getMessage());
        }
    }
 
}

Other classes for File Manipulation java.nio.file.Files - copy / delete java.nio.file.Paths - Path object to represent file Paths

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
 
public class FilesClassDemo {
 
    public static void main(String[] args) throws IOException{
        Files.copy(Paths.get("data/fruits.txt"), Paths.get("temp/fruits2.txt"));
        Files.delete(Paths.get("temp/fruits2.txt"));
    }
 
}