Tutorial on Converting an List of Strings or Numbers to a CSV file with optional sorting

Chances are you might have needed to convert a list of strings or numbers to a CSV file while you were programming something. An example is that in any java program you might have obtained a list of states of United States stored in your ArrayList object and then you wanted to have them in a CSV format so that you probably could load it to a database or use it for some other purposes.

I wrote this tool to serve the same purpose.

Here are the basic features this simple java example can do. Given a list of String objects stored in an ArrayList, this program can:

  • Convert Strings or numbers stored in an ArrayList object to comma separated strings
  • Print the comma separated values (CSV) to either console or file
  • Optionally you can sort the the list before you do the conversion.

package com.kushal.tools;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * @author Kushal Paudyal 
 * Last Modified on 2011-09-06 This utility converts a
 * list to comma separated values. Intended to be used with Strings and
 * can be modified with numbers.
 * 
 * Have options to write the converted values to either console or file.
 */
public class ListToCSV {
	private static boolean writeCSVToConsole = true;
	private static boolean writeCSVToFile = true;
	private static String destinationCSVFile = "C:\temp\convertedCSV.csv";
	private static boolean sortTheList = true;

	public static void main(String[] args) {
		ListToCSV util = new ListToCSV();
		List<String> sampleList = util.createSampleList();
		util.convertAndPrint(sampleList, writeCSVToConsole, writeCSVToFile, sortTheList);

	}

	/**
	 * @param sampleList - input list of string
	 * @param writeToConsole - if this flag is true, writes to console
	 * @param writeToFile - if this flag is true writes to file.
	 * @param sortTheList - if the list is to be sorted before conversion
	 */
	private void convertAndPrint(List<String> sampleList,
			boolean writeToConsole, boolean writeToFile, boolean sortTheList) {
		String commaSeparatedValues = "";

		/** If the list is not null and the list size is not zero, do the processing**/
		if (sampleList != null) {
			/** Sort the list if sortTheList was passed as true**/
			if(sortTheList) {
				Collections.sort(sampleList);
			}
			/**Iterate through the list and append comma after each values**/
			Iterator<String> iter = sampleList.iterator();
			while (iter.hasNext()) {
				commaSeparatedValues += iter.next() + ",";
			}
			/**Remove the last comma**/
			if (commaSeparatedValues.endsWith(",")) {
				commaSeparatedValues = commaSeparatedValues.substring(0,
						commaSeparatedValues.lastIndexOf(","));
			}
		}
		/** If writeToConsole flag was passed as true, output to console**/
		if(writeToConsole) {
			System.out.println(commaSeparatedValues);
		}
		/** If writeToFile flag was passed as true, output to File**/		
		if(writeToFile) {
			try {
				FileWriter fstream = new FileWriter(destinationCSVFile, false);
				BufferedWriter out = new BufferedWriter(fstream);
				out.write(commaSeparatedValues);
				out.close();
				System.out.println("*** Also wrote this information to file: " + destinationCSVFile);
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

	}

	/**
	 * Creates a sample list to be used by the convertAndPrint method
	 * and returns it to the calling method. 
	 */
	private List<String> createSampleList() {
		List<String> sampleList = new ArrayList<String>();
		sampleList.add("Nebraska");
		sampleList.add("Iowa");
		sampleList.add("Illinois");
		sampleList.add("Idaho");
		return sampleList;
	}
}

Java Static Import Explained With Easy Example With Source Code

What is Static Import?

Static Import is a feature in Java that allows you to access the methods and variables that are defined as public static to be used in a class without having to use the class name.

Let’s say there is a following class with a static field and a static method.

package com.sample;
public Class MyClassOne() {
	public static int a_number = 3;
	
	public static void doSomething(int number) {
		System.out.println("Did Something " + number);
	}
}


Now let’s create another class that use variable and method from this class. I am not suggesting you should make your variable public – this is for demonstration purpose only. A good programming practice is to declare your variables private and expose them via getters and setters method as necessary.

Regular Way (Non Static Import)

package com.sampletwo;

import com.sample.MyClassOne;

public Class MyClassTwo() {
	
	
	public static void doSomethingTwo() {
		MyClassOne.doSoemthing(MyClassOne.a_number);
	}
}


With Static Import, the code becomes

package com.sampletwo;

import com.sample.MyClassOne.*;

public Class MyClassTwoStatic() {
	
	
	public static void doSomethingTwo() {
		doSomething(a_number);
	}
}


Note: Do not statically import methods with a name that is identical to a method in Object, because methods that are naturally in scope take precedence over static imports

Calling URL Browser From Java Application

This program teaches you how you can call the browser in your OS to open the URL that you are passing from your Java application. This program is fully compiled and tested.

package com.kushal.utilities;

/**
 * @author Kushal Paudyal
 * www.sanjaal.com/java
 * Last Modified On: 26th August, 2008
 */
import java.lang.reflect.Method;

import javax.swing.JOptionPane;

public class OpenDefaultBrowserFromJava {
	private static final String errMsg = "ERROR WHILE ATTEMPTEING TO LUNCH WEB BROWSER";
	private static final String errFindingBrowser="COULD NOT FIND THE BROWSER";
	
	public static void main(String args [])
	{
		String urlToOpen="http://www.sanjaal.com/java";
		openURL(urlToOpen);
	}

	/**
	 * This method takes URL as a parameter and tries to
	 * identify Operating system and then lunches the broswer
	 * with the given URL
	 */
	public static void openURL(String url) {
		String operatingSystem = System.getProperty("os.name");
		try {
			/*
			 * Check if it is windows OS 
			 */
			if (operatingSystem.startsWith("Windows"))
				Runtime.getRuntime().exec("rundll32 url.dll,FileProtocolHandler " + url);
			/*
			 * If not windows OS, Check if it is a Mac OS
			 */
			else if (operatingSystem.startsWith("Mac OS")) {
				Class fileManager = Class.forName("com.apple.eio.FileManager");
				Method openURL = fileManager.getDeclaredMethod("openURL",
						new Class[] { String.class });
				openURL.invoke(null, new Object[] { url });
			}
			
			/*
			 * Or, it might be some unix or linux OS
			 */
			else { 
				/**
				 * There are different browsers possible.
				 */
				String[] browsers = { 	"firefox", 
										"netscape",
										"opera", 
										"konqueror", 
										"epiphany", 
										"mozilla"};
				String browser = null;
				
				for (int count = 0; count < browsers.length && browser == null; count++)
					if (Runtime.getRuntime().exec(
							new String[] { "which", browsers[count] })
							.waitFor() == 0)
						browser = browsers[count];

				if (browser == null) 
					throw new Exception(errFindingBrowser);
				else
					Runtime.getRuntime().exec(new String[] { browser, url });
			}

		} catch (Exception e) {
			JOptionPane.showMessageDialog(null, errMsg + ":n" + e.getMessage());
		}
	}

}