How to read and write text, Excel and CSV file in java?.

Write and Read Text txt file.

 import java.io.BufferedReader;  
 import java.io.BufferedWriter;  
 import java.io.File;  
 import java.io.FileNotFoundException;  
 import java.io.FileReader;  
 import java.io.FileWriter;  
 import java.io.IOException;  
 public class WriteandReadFile {  
   static File file;  
   public static void main(String[] a) throws FileNotFoundException, IOException {  
     try {  
       file = new File("writetextfile.txt");  
       // if file doesnt exists, then create it  
       if (!file.exists()) {  
         file.createNewFile();  
       }  
       // Write text on txt file.  
       FileWriter fw = new FileWriter(file, true);  
       BufferedWriter bw = new BufferedWriter(fw);  
       bw.write("How to write and read text file in java\n");  
       bw.close();  
     } catch (IOException e) {  
       e.printStackTrace();  
     }  
     // Read text from file.    
     FileReader fr = new FileReader(file);  
     BufferedReader br = new BufferedReader(fr);  
     String st;  
     while ((st = br.readLine()) != null) {  
       System.out.println(st);  
     }  
   }  
 }  

Write and Read data Excel file.

Download jxl.jar

 import java.io.File;  
 import java.io.IOException;  
 import jxl.Sheet;  
 import jxl.Workbook;  
 import jxl.read.biff.BiffException;  
 import jxl.write.Label;  
 import jxl.write.WritableSheet;  
 import jxl.write.WritableWorkbook;  
 import jxl.write.WriteException;  
 import jxl.write.Number;  
 public class ReadandWriteExcelFile {  
   public static void main(String[] args) throws BiffException, IOException, WriteException {  
     File file = new File("output.xls");  
     // if file doesnt exists, then create it  
     if (!file.exists()) {  
       file.createNewFile();  
     }  
     // Write Excel file using jxl api  
     WritableWorkbook wworkbook;  
     wworkbook = Workbook.createWorkbook(file);  
     WritableSheet wsheet = wworkbook.createSheet("First Sheet", 0);  
     for (int rows = 0; rows < 10; rows++) {  
       wsheet.addCell(new Label(0, rows, "First Coloum " + rows));  
       wsheet.addCell(new Number(1, rows, 3.1459 + rows));  
       wsheet.addCell(new Label(2, rows, "third Coloum " + rows));  
       wsheet.addCell(new Number(3, rows, 7895 + rows));  
     }  
     wworkbook.write();  
     wworkbook.close();  
     // Read Excel file using jxl api  
     Workbook workbook = Workbook.getWorkbook(file);  
     Sheet sh = workbook.getSheet(0);  
     for (int rows = 0; rows < sh.getRows(); rows++) {  
       for (int colm = 0; colm < sh.getColumns(); colm++) {  
    System.out.print(sh.getCell(colm, rows).getContents() + " ");  
       }  
       System.out.println();  
     }  
   }  
 }  

Write and Read data CSV file.

Download javacsv.jar

 import com.csvreader.CsvWriter;  
 import java.io.BufferedReader;  
 import java.io.File;  
 import java.io.FileNotFoundException;  
 import java.io.FileReader;  
 import java.io.FileWriter;  
 import java.io.IOException;  
 public class ReadandWriteCSVFile {  
   public static void main(String[] args) throws FileNotFoundException, IOException {  
     boolean alreadyExists = new File("Output.csv").exists();  
     try {  
  // use FileWriter constructor that specifies open for appending  
 CsvWriter csvOutput = new CsvWriter(new FileWriter("Output.csv",true),',');  
 // if the file didn't already exist then we need to write out the header line  
       if (!alreadyExists) {  
         csvOutput.write("Name");  
         csvOutput.write("Deparment");  
         csvOutput.write("Year");  
         csvOutput.endRecord();  
       }  
       // write out a few records  
       for (int i = 0; i < 10; i++) {  
         csvOutput.write("Studen " + i);  
         csvOutput.write("Deparment " + i);  
         csvOutput.write("201" + i);  
         csvOutput.endRecord();  
       }  
       csvOutput.close();  
     } catch (IOException e) {  
       e.printStackTrace();  
     }  
     // Read data from CSV file.    
     FileReader fr = new FileReader(new File("Output.csv"));  
     BufferedReader br = new BufferedReader(fr);  
     String st;  
     while ((st = br.readLine()) != null) {  
       System.out.println(st);  
     }  
   }  
 }