Author: admin

1. Hello World
2. Hello World with Servlet Web
3. Template Directives
4. Predefined Template Directives
5. User Defined Directives

package com.demo;

import java.io.IOException;
import com.csvreader.CsvWriter;

public class ArrayToCSVDemo {

  public static void main(String[] args) {
    
    String array[] = {"Suryanagar, Vikhroli", "Java", "SQL", "13"};
    
    try {
      
      CsvWriter writer = new CsvWriter("awesomefile.csv");
      
      writer.writeRecord(array);
      
      writer.close();
      
    } catch (IOException e) {

      e.printStackTrace();
    }
    
  }

}

Reference Link: http://www.journaldev.com/12014/opencsv-csvreader-csvwriter-example

Jar File: http://www.java2s.com/Code/Jar/j/Downloadjavacsvjar.htm

Using FileWriter class

import java.io.FileWriter;

public class TestFileWriter {

  public static String implodeString(String[] split) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < split.length; i++) {			
        sb.append(split[i]);
        if (i != split.length - 1) {
            sb.append("\",\"");
        }
    }
    return "\"" . concat(sb.toString()) .concat("\"");
  }
  
  public static void main(String[] args) {
    
    String array[] = {"Suryanagar, Vikhroli", "Java", "SQL", "13"};
    
    try {
      
      FileWriter fw = new FileWriter("testout.csv");
      //fw.write("\"Suryanagar, Vikhroli\", Java, SQL, 13");
      fw.write(implodeString(array));
      fw.close();
    } catch (Exception e) {
      System.out.println(e);
    }

    System.out.println("Success...");

  }

}

Prerequisite
Download all poi jar files
https://poi.apache.org/download.html

1.  Terms
   • Workbook – The file contains number of sheets
   • Sheet – Matrix contains rows and cell
   • Row – Record of an entity in one row
   • Cell – A single cell which hold value

2. JFileChooser fileChooser = new JFileChooser();
           int returnValue = fileChooser.showDialog(null, "Select File");
           
           if(returnValue == JFileChooser.APPROVE_OPTION) {
               Workbook workbook = new HSSFWorkbook(new FileInputStream(fileChooser.getSelectedFile()));
               
               Sheet sheet = workbook.getSheetAt(0);
               
               for(Iterator<Row> rit = sheet.rowIterator(); rit.hasNext();){
                   for(Iterator<Cell> cit = rit.next().cellIterator(); cit.hasNext();){
                       System.out.println(cit.next());
                   }
                   System.out.println("");
               }
           } else {
               System.out.println("Invalid output");
           }

3. JFileChooser fileChooser = new JFileChooser();
           int returnValue = fileChooser.showDialog(null, "Select File");
           
           if(returnValue == JFileChooser.APPROVE_OPTION) {
               FileInputStream excelFile = new FileInputStream(fileChooser.getSelectedFile());
               Workbook workbook = new XSSFWorkbook(excelFile);
               
               Sheet sheet = workbook.getSheetAt(0);
               
               for(Iterator<Row> rit = sheet.rowIterator(); rit.hasNext();) {
                   for(Iterator<Cell> cit = rit.next().cellIterator(); cit.hasNext();) {
                       System.out.print(cit.next() + "\t" + cit.next());
                   }
                   System.out.println("");
               }
           }

4.  Workbook workbook = new HSSFWorkbook();
           
           Sheet sheet1 = workbook.createSheet("movies");
   //        Sheet sheet2 = workbook.createSheet("Test Cases");
   //        Sheet sheet3 = workbook.createSheet(WorkbookUtil.createSafeSheetName("$*(^&?"));
           
           Row row = sheet1.createRow(0);
           
   //        Cell cell = row.createCell(4);
   //        cell.setCellValue("Hello World");
   //        Cell cell2 = row.createCell(3);
   //        cell2.setCellValue("terminator");
   //        System.out.println(cell.getRichStringCellValue().toString());
   //        System.out.println(cell2.getRichStringCellValue().toString());
   
           Cell cell1 = row.createCell(0);
           Cell cell2 = row.createCell(1);
           Cell cell3 = row.createCell(2);
           Cell cell4 = row.createCell(3);
           Cell cell5 = row.createCell(4);
           
           cell1.setCellValue(5);
           cell2.setCellValue("+");
           cell3.setCellValue(6);
           cell4.setCellValue("=");
           cell5.setCellFormula("A1+C1");
           
           try {
               FileOutputStream outputStream = new FileOutputStream("test1.xlsx");
               workbook.write(outputStream);
               outputStream.close();
           } catch (Exception e) {
               e.printStackTrace();
           }

5.  Complete Program

   import java.io.FileInputStream;
   import java.io.FileNotFoundException;
   import java.io.FileOutputStream;
   import java.io.IOException;
   import java.util.Iterator;
   import javax.swing.JFileChooser;
   import org.apache.poi.hssf.usermodel.HSSFWorkbook;
   import org.apache.poi.ss.usermodel.Workbook;
   import org.apache.poi.ss.usermodel.Sheet;
   import org.apache.poi.ss.util.WorkbookUtil;
   import org.apache.poi.ss.usermodel.Row;
   import org.apache.poi.ss.usermodel.Cell;
   import org.apache.poi.xssf.usermodel.XSSFWorkbook;
   
   /**
    *
    * @author Shailesh Sonare
    */
   public class ApachePOIDemo {
   
       /**
        * @param args the command line arguments
        */
       public static void main(String[] shailesh) throws IOException {
           
           /*
           
           Workbook workbook = new HSSFWorkbook();
           
           Sheet sheet1 = workbook.createSheet("movies");
   //        Sheet sheet2 = workbook.createSheet("Test Cases");
   //        Sheet sheet3 = workbook.createSheet(WorkbookUtil.createSafeSheetName("$*(^&?"));
           
           Row row = sheet1.createRow(0);
           
   //        Cell cell = row.createCell(4);
   //        cell.setCellValue("Hello World");
   //        Cell cell2 = row.createCell(3);
   //        cell2.setCellValue("terminator");
   //        System.out.println(cell.getRichStringCellValue().toString());
   //        System.out.println(cell2.getRichStringCellValue().toString());
   
           Cell cell1 = row.createCell(0);
           Cell cell2 = row.createCell(1);
           Cell cell3 = row.createCell(2);
           Cell cell4 = row.createCell(3);
           Cell cell5 = row.createCell(4);
           
           cell1.setCellValue(5);
           cell2.setCellValue("+");
           cell3.setCellValue(6);
           cell4.setCellValue("=");
           cell5.setCellFormula("A1+C1");
           
           try {
               FileOutputStream outputStream = new FileOutputStream("test1.xlsx");
               workbook.write(outputStream);
               outputStream.close();
           } catch (Exception e) {
               e.printStackTrace();
           }
           */
           /*
           JFileChooser fileChooser = new JFileChooser();
           int returnValue = fileChooser.showDialog(null, "Select File");
           
           if(returnValue == JFileChooser.APPROVE_OPTION) {
               Workbook workbook = new HSSFWorkbook(new FileInputStream(fileChooser.getSelectedFile()));
               
               Sheet sheet = workbook.getSheetAt(0);
               
               for(Iterator<Row> rit = sheet.rowIterator(); rit.hasNext();){
                   for(Iterator<Cell> cit = rit.next().cellIterator(); cit.hasNext();){
                       System.out.println(cit.next());
                   }
                   System.out.println("");
               }
           } else {
               System.out.println("Invalid output");
           }
           */
           
           JFileChooser fileChooser = new JFileChooser();
           int returnValue = fileChooser.showDialog(null, "Select File");
           
           if(returnValue == JFileChooser.APPROVE_OPTION) {
               FileInputStream excelFile = new FileInputStream(fileChooser.getSelectedFile());
               Workbook workbook = new XSSFWorkbook(excelFile);
               
               Sheet sheet = workbook.getSheetAt(0);
               
               for(Iterator<Row> rit = sheet.rowIterator(); rit.hasNext();) {
                   for(Iterator<Cell> cit = rit.next().cellIterator(); cit.hasNext();) {
                       System.out.print(cit.next() + "\t" + cit.next());
                   }
                   System.out.println("");
               }
           }
           
       }    
   }
   

    

    

class A {
    public void test(){
        System.out.println("hello");
    }
    
    public void foo(){
        System.out.println("fooo");
    }
}

class B extends A {
    @Override
    public void test(){
        System.out.println("world");
    }
    public void bar(){
        System.out.println("baar");
    }
}


public class PolymorphismDemo {

    public static void main(String[] args) {
        
        A a = new A();
        a.test(); // allowed: will print hello
        a.foo(); // allowed: will print fooo
        //a.bar(); // not allowed: compile time error
        
        B b = new B();
        b.test(); // allowed: will print world
        b.foo(); // allowed: will print fooo
        b.bar(); // allowed: will print baar
        
        A c = new B();
        c.test(); // allowed: will print world
        c.foo(); // allowed: will print fooo
        //c.bar(); // not allowed: compile time error
        
        //B d = new A(); // not allowed: compile time error
        
        A e = new B();
        A f = (A)e;
        f.test(); // allowed: will print world
        f.foo(); // allowed: will print fooo
        //f.bar(); // not allowed: compile time error
        
        B g = new B();
        A h = (A)g;
        h.test(); // allowed: will print world
        h.foo(); // allowed: will print fooo
        //h.bar(); // not allowed: compile time error
    }    
}