Programming Fundamentals Lab Manual 12

Statement Purpose:

The java.io package contains nearly every class you might ever need to perform input and output (I/O) in Java. All these streams represent an input source and an output destination. The stream in the java.io package supports many data such as primitives, object, localized characters, etc.

Activity Outcomes:

Student will be able to:

• • • • • • • • • Describe the concept of an I/O stream
                • Explain the difference between text files and binary files
                • Save data
                • Read data

1)       Stage J (Journey)

2)    Stage a1 (apply)

Lab Activities:

Activity 1:

Write a java program to get a files size in bytes?

Solution:

import java.io.File;

 public class Main 
{  
   public static long getFileSize(String filename) 
               {         File file = new File(filename);      
                             if (!file.exists() || !file.isFile()) 
                                      {          System.out.println("File doesn\'t exist"); 
                                                 return -1;
 
                                       }       return file.length();

                }    public static void main(String[] args)
                                        {       long size = getFileSize("c:/java.txt");

                                             System.out.println("Filesize in bytes: " + size);

                 }

}

Activity 2:

Write a java program to get a files size in bytes?

Solution:

import java.io.File;

 public class Main {    public static long getFileSize(String filename)
                         {       File file = new File(filename);   
                                   if (!file.exists() || !file.isFile()) {

         System.out.println("File doesn\'t exist");

  return -1;

      }       return file.length();

   }    public static void main(String[] args) {       long size = getFileSize("c:/java.txt");

      System.out.println("Filesize in bytes: " + size);

   }

}

Activity 3:

Write a java program to change the last modification time of a file?

Solution:

import java.io.File; import java.util.Date;

 public class Main {    public static void main(String[] args) throws Exception
                           {       File fileToChange = new File ("C:/myjavafile.txt");   
                                   fileToChange.createNewFile();

                                   Date filetime = new Date (fileToChange.lastModified());

                                   System.out.println(filetime.toString());

                                   System.out.println (fileToChange.setLastModified

                                  (System.currentTimeMillis()));   
                                  filetime = new Date (fileToChange.lastModified());

                                 System.out.println(filetime.toString());

   }

}

Activity 4:

Write a java program to create a temporary file?

Solution:

import java.io.*;

public class Main 
{  
  public static void main(String[] args) throws Exception 
   {   
                                  File temp = File.createTempFile ("pattern", ".suffix");     
                                  temp.deleteOnExit(); 

                                  BufferedWriter out = new BufferedWriter (new FileWriter(temp));       
                                  out.write("aString");

                                  System.out.println("temporary file created:");      
                                  out.close();

   }

}

Activity 5:

Write a java program to append a string in an existing file?

Solution:

import java.io.*;

 public class Main
{    public static void main(String[] args) throws Exception
    {       try 
        {

         BufferedWriter out = new BufferedWriter(new FileWriter("filename"));        
         out.write("aString1\n");          out.close();       
         out = new BufferedWriter(new FileWriter("filename",true));     

          out.write("aString2");          out.close();

         BufferedReader in = new BufferedReader(new FileReader("filename"));

         String str;

                   while ((str = in.readLine()) != null) {

            System.out.println(str);

         }       }       in.close();       catch (IOException e) {

         System.out.println("exception occoured"+ e);

      }

   }

}

 

3)    Stage v (verify)

Home Activities:

Activity 1: Write a java program to copy one file into another file?

Activity 2:  Write a java program to delete a file?

4)    Stage a2 (assess)

Assignment:

• Write a java program to read a file?
• Write a java program to write into a file?