Reverse Array Elements in Java

Reverse Array Elements in Java

public class ReverseArray {

       public static void main(String[] args) {

              int[] intArr = new int[] { 1, 2, 3, 4, 5, 6, 7 };

              System.out.println("Array elements before reverse");

              displayArrayElements(intArr);

              reverseArrayElements(intArr);

              System.out.println("reversed array elements");

              displayArrayElements(intArr);

       }

       public static void displayArrayElements(int[] arr) {

              for (int temp : arr) {

                     System.out.println(temp);

              }

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

       }

       public static void reverseArrayElements(int[] arr) {

              int temp = 0;

              for (int start = 0, end = arr.length - 1; start < end; start++, end--) {

                     temp = arr[start];

                     arr[start] = arr[end];

                     arr[end] = temp;

              }

       }

}

output

Array elements before reverse
1
2
3
4
5
6
7
..............................
reversed array elements
7
6
5
4
3
2
1
..............................

Find Minimum and Maximum value of Array in Java

Find Minimum and Maximum value of Array in Java

public class FindMinAndMaxValueInArray {

       public static void main(String[] args) {

              int arr[] = { 69, 23, 47, 81, 92, 88, 52, 48, 56, 66, 65, 76, 71, 85,

                           49, 53, 56, 61, 65, 84 };

              findMaxValue(arr);

              findMinValue(arr);

       }

       public static void findMinValue(int[] arr) {

              int min = arr[0];

              for (int i = 0; i < arr.length; i++) {

                     if (min > arr[i]) {

                           min = arr[i];

                     }

              }

              System.out.println("minimum value of the array is:" + min);

       }

       public static void findMaxValue(int[] arr) {

              int max = arr[0];

              for (int i = 0; i < arr.length; i++) {

                     if (max < arr[i]) {

                           max = arr[i];

                     }

              }

              System.out.println("maximum value of array is:" + max);

       }

}

output

maximum value of array is:92
minimum value of the array is:23

Find Duplicates in an array

Find Duplicates in an array

package com.blogspot.rajvishwakarma15;

public class CheckDuplictesInArray {

       public static void main(String[] args) {

              String[] strArr = new String[] { "a", "b", "c", "s", "d", "e", "a",

                           "b", "s" };

              detectDuplicates(strArr);

       }

       public static void detectDuplicates(String[] arr) {

              for (int i = 0; i < arr.length; i++) {

                     for (int j = i + 1; j < arr.length; j++) {

                           if (arr[j] == arr[i]) {

                      System.out.println("Duplicate found! Original was at location "

                               + (i + 1) + " and match is at " + (j + 1));

                                  System.out.println("Duplicated value is:" + arr[j]);

                           }

                     }

              }

       }

}

OUTPUT

Duplicate found! Original was at location 1 and match is at 7 Duplicated value is:a

Duplicate found! Original was at location 2 and match is at 8 Duplicated value is:b

Duplicate found! Original was at location 4 and match is at 9 Duplicated value is:s

File Upload in JSP

A JSP can be used with an HTML form tag to allow users to upload files to the server. An uploaded file could be a text file or binary or image file or any document.

Creating a File Upload Form:

The following HTM code below creates an uploader form. Following are the important points to be noted down:

• The form method attribute should be set to POST method and GET method can not be used.
• The form enctype attribute should be set to multipart/form-data.
• The form action attribute should be set to a JSP file which would handle file uploading at backend server. Following example is using uploadFile.jsp program file to upload file.
• To upload a single file you should use a single <input .../> tag with attribute type="file". To allow multiple files uploading, include more than one input tags with different values for the name attribute. The browser associates a Browse button with each of them.

 
<html>
<head>
<title>File Uploading Form</title>
</head>
<body>
<h3>File Upload:</h3>
Select a file to upload: <br />
<form action="UploadServlet" method="post"
                        enctype="multipart/form-data">
<input type="file" name="file" size="50" />
<br />
<input type="submit" value="Upload File" />
</form>
</body>
</html>

This will display following result which would allow to select a file from local PC and when user would click at "Upload File", form would be submitted along with the selected file:

 
File Upload: 
Select a file to upload: 
 
 

 
 

 

NOTE: Above form is just dummy form and would not work, you should try above code at your machine to make it work.

Writing Backend JSP Script:

First let us define a location where uploaded files would be stored. You can hard code this in your program or this directory name could also be added using an external configuration such as a context-param element in web.xml as follows:

 
<web-app>
....
<context-param> 
    <description>Location to store uploaded file</description> 
    <param-name>file-upload</param-name> 
    <param-value>
         c:\apache-tomcat-5.5.29\webapps\data\
     </param-value> 
</context-param>
....
</web-app>

Following is the source code for UploadFile.jsp which can handle multiple file uploading at a time. Before proceeding you have make sure the followings:

• Following example depends on FileUpload, so make sure you have the latest version ofcommons-fileupload.x.x.jar file in your classpath. You can download it fromhttp://commons.apache.org/fileupload/.
• FileUpload depends on Commons IO, so make sure you have the latest version of commons-io-x.x.jar file in your classpath. You can download it from http://commons.apache.org/io/.
• While testing following example, you should upload a file which has less size than maxFileSizeotherwise file would not be uploaded.
• Make sure you have created directories c:\temp and c:\apache-tomcat-5.5.29\webapps\data well in advance.

<%@ page import="java.io.*,java.util.*, javax.servlet.*" %>
<%@ page import="javax.servlet.http.*" %>
<%@ page import="org.apache.commons.fileupload.*" %>
<%@ page import="org.apache.commons.fileupload.disk.*" %>
<%@ page import="org.apache.commons.fileupload.servlet.*" %>
<%@ page import="org.apache.commons.io.output.*" %>

<%
   File file ;
   int maxFileSize = 5000 * 1024;
   int maxMemSize = 5000 * 1024;
   ServletContext context = pageContext.getServletContext();
   String filePath = context.getInitParameter("file-upload");

   // Verify the content type
   String contentType = request.getContentType();
   if ((contentType.indexOf("multipart/form-data") >= 0)) {

      DiskFileItemFactory factory = new DiskFileItemFactory();
      // maximum size that will be stored in memory
      factory.setSizeThreshold(maxMemSize);
      // Location to save data that is larger than maxMemSize.
      factory.setRepository(new File("c:\\temp"));

      // Create a new file upload handler
      ServletFileUpload upload = new ServletFileUpload(factory);
      // maximum file size to be uploaded.
      upload.setSizeMax( maxFileSize );
      try{ 
         // Parse the request to get file items.
         List fileItems = upload.parseRequest(request);

         // Process the uploaded file items
         Iterator i = fileItems.iterator();

         out.println("<html>");
         out.println("<head>");
         out.println("<title>JSP File upload</title>");  
         out.println("</head>");
         out.println("<body>");
         while ( i.hasNext () ) 
         {
            FileItem fi = (FileItem)i.next();
            if ( !fi.isFormField () ) 
            {
            // Get the uploaded file parameters
            String fieldName = fi.getFieldName();
            String fileName = fi.getName();
            boolean isInMemory = fi.isInMemory();
            long sizeInBytes = fi.getSize();
            // Write the file
            if( fileName.lastIndexOf("\\") >= 0 ){
            file = new File( filePath + 
            fileName.substring( fileName.lastIndexOf("\\"))) ;
            }else{
            file = new File( filePath + 
            fileName.substring(fileName.lastIndexOf("\\")+1)) ;
            }
            fi.write( file ) ;
            out.println("Uploaded Filename: " + filePath + 
            fileName + "<br>");
            }
         }
         out.println("</body>");
         out.println("</html>");
      }catch(Exception ex) {
         System.out.println(ex);
      }
   }else{
      out.println("<html>");
      out.println("<head>");
      out.println("<title>Servlet upload</title>");  
      out.println("</head>");
      out.println("<body>");
      out.println("<p>No file uploaded</p>"); 
      out.println("</body>");
      out.println("</html>");
   }
%>

Now try to upload files using the HTML form which you created above. When you would try http://localhost:8080/UploadFile.htm, it would display following result which would help you uploading any file from your local machine.

 
File Upload: 
Select a file to upload: 
 
 

 
 

If your JSP script works fine, your file should be uploaded in c:\apache-tomcat-5.5.29\webapps\data\ directory.

Ref. => javatpoint.com