Comparing Objects in Java

In Java comparing two value object is not straight forward. Here we will see how we can compare two value objects in Java.

For that first we will create a value object called “MyValueObject”. This value object contains two properties. 1) firstName 2) lastName. Both the properties are of type string.

In the same class we also have a overridden method which does the comparison for us. This method “public boolean equals(Object obj)” takes the properties and compare them individually. if the properties values are all equal then it returns true or it will return false. By doing this our test class will just call the equals method on the object to make sure if the objects are equal or not.

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package com.blogspot.javawave;
 
/**
 *
 * @author dhanago
 */
public class MyValueObject
{
 
    private String firstName;
    private String lastName;
 
    /**
     * This constructor is used to set the two properties values in the class.
     *
     * @param firstName
     * @param lastName
     */
    public MyValueObject(String firstName,
                          String lastName)
    {
        this.firstName = firstName;
        this.lastName = lastName;
    }
 
    @Override
    public boolean equals(Object obj)
    {
        boolean isEqual = false;
        if (this.getClass() == obj.getClass())
        {
            MyValueObject myValueObject = (MyValueObject) obj;
            if ((myValueObject.firstName).equals(this.firstName) &&
                    (myValueObject.lastName).equals(this.lastName))
            {
                isEqual = true;
            }
        }
 
        return isEqual;
    }
}
Test class is given below:
 
 
/*
 */
package com.blogspot.javawave;
 
/**
 *This class is used to test compare the value object.
 *
 * @author dhanago
 */
public class TestCompareValueObject
{
 
    /**
     * This is the main method used to test compare the value object.
     * @param arg
     */
    public static void main(String[] arg)
    {
        MyValueObject obj1 = new MyValueObject("Muthu", "Kumar");
        MyValueObject obj2 = new MyValueObject("Muthu", "Kumar");
 
        if (obj1.equals(obj2))
        {
            System.out.println("Both the objects are equal");
        }
        else
        {
            System.out.println("Both the objects are not equal");
        }
    }
}

This one of the way we can easily compare the value objects in Java.

Note : This article is originally published in : http://javawave.blogspot.com.
Republished here with author’s permission.

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• Copying File Contents using FileChannel
• Randomly accessing the file contents

If you have any doubts on the code and looking for the help on this code, please post your queries in the comments section.

File Upload and Download Code Example

package com.resource.util;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

/**
 * This class is used to upload a file to a FTP server.
 *
 * @author Muthu
 */
public class FileUpload
{

   /**
    * Upload a file to a FTP server. A FTP URL is generated with the
    * following syntax:
    * ftp://user:password@host:port/filePath;type=i.
    *
    * @param ftpServer , FTP server address (optional port ':portNumber').
    * @param user , Optional user name to login.
    * @param password , Optional password for user.
    * @param fileName , Destination file name on FTP server (with optional
    *            preceding relative path, e.g. "myDir/myFile.txt").
    * @param source , Source file to upload.
    * @throws MalformedURLException, IOException on error.
    */
   public void upload( String ftpServer, String user, String password,
         String fileName, File source ) throws MalformedURLException,
         IOException
   {
      if (ftpServer != null && fileName != null && source != null)
      {
         StringBuffer sb = new StringBuffer( "ftp://" );
         // check for authentication else assume its anonymous access.
         if (user != null && password != null)
         {
            sb.append( user );
            sb.append( ':' );
            sb.append( password );
            sb.append( '@' );
         }
         sb.append( ftpServer );
         sb.append( '/' );
         sb.append( fileName );
         /*
          * type ==> a=ASCII mode, i=image (binary) mode, d= file directory
          * listing
          */
         sb.append( ";type=i" );

         BufferedInputStream bis = null;
         BufferedOutputStream bos = null;
         try
         {
            URL url = new URL( sb.toString() );
            URLConnection urlc = url.openConnection();

            bos = new BufferedOutputStream( urlc.getOutputStream() );
            bis = new BufferedInputStream( new FileInputStream( source ) );

            int i;
            // read byte by byte until end of stream
            while ((i = bis.read()) != -1)
            {
               bos.write( i );
            }
         }
         finally
         {
            if (bis != null)
               try
               {
                  bis.close();
               }
               catch (IOException ioe)
               {
                  ioe.printStackTrace();
               }
            if (bos != null)
               try
               {
                  bos.close();
               }
               catch (IOException ioe)
               {
                  ioe.printStackTrace();
               }
         }
      }
      else
      {
         System.out.println( "Input not available." );
      }
   }

   /**
    * Download a file from a FTP server. A FTP URL is generated with the
    * following syntax:
    * ftp://user:password@host:port/filePath;type=i.
    *
    * @param ftpServer , FTP server address (optional port ':portNumber').
    * @param user , Optional user name to login.
    * @param password , Optional password for user.
    * @param fileName , Name of file to download (with optional preceeding
    *            relative path, e.g. one/two/three.txt).
    * @param destination , Destination file to save.
    * @throws MalformedURLException, IOException on error.
    */
   public void download( String ftpServer, String user, String password,
         String fileName, File destination ) throws MalformedURLException,
         IOException
   {
      if (ftpServer != null && fileName != null && destination != null)
      {
         StringBuffer sb = new StringBuffer( "ftp://" );
         // check for authentication else assume its anonymous access.
         if (user != null && password != null)
         {
            sb.append( user );
            sb.append( ':' );
            sb.append( password );
            sb.append( '@' );
         }
         sb.append( ftpServer );
         sb.append( '/' );
         sb.append( fileName );
         /*
          * type ==> a=ASCII mode, i=image (binary) mode, d= file directory
          * listing
          */
         sb.append( ";type=i" );
         BufferedInputStream bis = null;
         BufferedOutputStream bos = null;
         try
         {
            URL url = new URL( sb.toString() );
            URLConnection urlc = url.openConnection();

            bis = new BufferedInputStream( urlc.getInputStream() );
            bos = new BufferedOutputStream( new FileOutputStream(
                  destination.getName() ) );

            int i;
            while ((i = bis.read()) != -1)
            {
               bos.write( i );
            }
         }
         finally
         {
            if (bis != null)
               try
               {
                  bis.close();
               }
               catch (IOException ioe)
               {
                  ioe.printStackTrace();
               }
            if (bos != null)
               try
               {
                  bos.close();
               }
               catch (IOException ioe)
               {
                  ioe.printStackTrace();
               }
         }
      }
      else
      {
         System.out.println( "Input not available" );
      }
   }
}