File Handling

File Writer 


How to use existing Java API for writing data to external file for persistance.

Source: TestFileWriter.java

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

public class TestFileWriter {

    public static void main(String[] args) {

    try {

            FileWriter writer = new FileWriter("c:/citydata.txt", true); //set true for append mode
            BufferedWriter bufferedWriter =new BufferedWriter(writer);
            bufferedWriter.write("Tokyo");
            bufferedWriter.write(",");
            bufferedWriter.write("New York");
            bufferedWriter.write(",");
            bufferedWriter.write("Colombo");
            bufferedWriter.write(",");
            bufferedWriter.write("Korea");
            bufferedWriter.write("\n");
            bufferedWriter.flush();
            bufferedWriter.close();
            writer.close();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

Output: 
After running above program check for creation of c:/citydata.txt with following contents


Tokyo, New York, Colombo, Korea
=================================================

File Reader 


How to use existing Java API for reading data from external file.

Source: TestFileReader.java

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;

public class TestFileReader {

    public static void main(String[] args) {
        File file = new File("c:/citydata.txt");

        try {

            Scanner scan = new Scanner(file);

            while (scan.hasNext()) {
                System.out.println(scan.nextLine());
            }       
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }

}

Output: 

Tokyo, New York, Colombo, Korea