Java Code House

Today I am going to post how you can display all the system properties with a simple Java program. You will need the java.util.Enumeration and java.util.Properties class. There is a method getProperties() defined in java.lang.System class. This method returns all the properties associated with your system as a Properties reference. Now we get an Enumeration of all keys of the properties. Next we iterate through each element of enumeration and get the value of individual keys and display them.
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import java.util.Enumeration;
import java.util.Properties;

public class SystemProperties{
public static void main (String[] args) {
Properties p=System.getProperties();  //getting system properties
Enumeration keys = p.keys();  //getting all keys of properties

        while (keys.hasMoreElements()) {
            String key = (String)keys.nextElement();  //getting next key
            String value = (String)p.get(key);  //getting key value
            System.out.println(key + ": " + value);
        }
    }
}
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java.runtime.name: Java(TM) SE Runtime Environment
sun.boot.library.path: C:\Program Files\Java\jdk1.7.0\jre\bin
java.vm.version: 21.0-b17
java.vm.vendor: Oracle Corporation
java.vendor.url: http://java.oracle.com/
path.separator: ;
java.vm.name: Java HotSpot(TM) Client VM
file.encoding.pkg: sun.io
user.country: US
user.script:
sun.java.launcher: SUN_STANDARD
sun.os.patch.level:
java.vm.specification.name: Java Virtual Machine Specification
user.dir: D:\Choto documents\Choto documents\Java Programs
java.runtime.version: 1.7.0-b147
java.awt.graphicsenv: sun.awt.Win32GraphicsEnvironment
java.endorsed.dirs: C:\Program Files\Java\jdk1.7.0\jre\lib\endorsed
os.arch: x86
java.io.tmpdir: C:\Users\Chelsea\AppData\Local\Temp\
line.separator:

java.vm.specification.vendor: Oracle Corporation
user.variant:
os.name: Windows 7
sun.jnu.encoding: Cp1252
java.library.path: C:\Program Files\Java\jdk1.7.0\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;C:\Program Files\PC Connectivity Solution\;C:\Program Files\Java\jdk1.7.0\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;.
java.specification.name: Java Platform API Specification
java.class.version: 51.0
sun.management.compiler: HotSpot Client Compiler
os.version: 6.1
user.home: C:\Users\Chelsea
user.timezone:
java.awt.printerjob: sun.awt.windows.WPrinterJob
file.encoding: Cp1252
java.specification.version: 1.7
java.class.path: D:\Java Programs;C:\Program Files\Java\jdk1.7.0\jre\lib\rt.jar;C:\Program Files\Java\jdk1.7.0\lib\dt.jar;C:\Program Files\Java\jdk1.7.0\lib\tools.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\ext\zipfs.jar
user.name: -MadMickael/FFF
java.vm.specification.version: 1.7
sun.java.command: SystemProperties
java.home: C:\Program Files\Java\jdk1.7.0\jre
sun.arch.data.model: 32
user.language: en
java.specification.vendor: Oracle Corporation
awt.toolkit: sun.awt.windows.WToolkit
java.vm.info: mixed mode, sharing
java.version: 1.7.0
java.ext.dirs: C:\Program Files\Java\jdk1.7.0\jre\lib\ext;C:\Windows\Sun\Java\lib\ext
sun.boot.class.path: C:\Program Files\Java\jdk1.7.0\jre\lib\resources.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\rt.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\sunrsasign.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\jce.jar;C:\Program Files\Java\jdk1.7.0\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.7.0\jre\classes
java.vendor: Oracle Corporation
file.separator: \
java.vendor.url.bug: http://bugreport.sun.com/bugreport/
sun.io.unicode.encoding: UnicodeLittle
sun.cpu.endian: little
sun.desktop: windows
sun.cpu.isalist: pentium_pro+mmx pentium_pro pentium+mmx pentium i486 i386 i86
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DOWNLOAD the source from 4shared

Today I am going to post a program that will be able to display i.e list all the files and folders in your computer. Here we have used the java.io.File class for this purpose. At first we call the listRoots() function to list all the drives. Then for each drive we list all of their contents. A recursive function is defined that takes in a reference of File class instance as parameter. Now if it is a file then its absolute path is displayed. If it is a folder then all the contents of this directory is listed and kept in a File array. Now for each of the elements of the array the recursive function is called. The contents are listed following DFS algorithm.
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import java.io.File;
public class FileList {

    static void list(File f){
        if (f.isFile()){
            System.out.println(f.getAbsolutePath()); //displays path for a file
            return;
        }
        else{
            File dir_list[]=f.listFiles();  //lists all contents if a directory
            for (File t : dir_list)
                try{
                  list(t);  //calls list for each content of directory
                }catch(Exception e){
                  e.printStackTrace();
                }
        }
    }
   
    public static void main(String[] args){
        File drive_list[]=File.listRoots();  //lists all drives
           try{
               for(File drive : drive_list)
                  list(drive);  //calls recur for each drive
            }catch(Exception e){
              e.printStackTrace();
            }       
    }
}
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DOWNLOAD the source from Mediafire
DOWNLOAD the source from 4shared

Today I am going to post how you can convert any image to gray scale in Java. First the image is read from a file using javax.imageio.ImageIO class as a BuffertedImage. A function is written that takes in a BufferedImage as parameter and returns a color converted image. An instance of java.awt.image.ColorConvertOp is created which takes in an object of java.awt.color.ColorSpace as first parameter and null as 2nd parameter( since there is no RenderingHints). Then the filter(src,dest) method is called which actually does the work. Then the final image is written to a file in jpeg format as dest.jpg .
How ColorCovertOp works : This class performs a pixel-by-pixel color conversion of the data in the source image. The resulting color values are scaled to the precision of the destination image. Color conversion can be specified via an array of ColorSpace objects or an array of ICC_Profile objects.
ColorSpace class : This is an abstract class whose getInstance(int) method is called to get an instance and CS_GRAY is passed as parameter which defines a built in linear gray scale color space.

Screenshots of images are shown below

Original image

Gray Scale image

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import java.io.File;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.color.ColorSpace;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import javax.imageio.ImageIO;

@SuppressWarnings("serial")
public class GrayScale extends JPanel{
    @Override
    public void paintComponent(Graphics g){
        Graphics2D g2d=(Graphics2D)g;
        try{   //reading from file
            BufferedImage src=ImageIO.read(new File("src.jpg"));
            BufferedImage dest=convertToGray(src);  //getting destination image
            g2d.drawImage(dest,0,0,this);  /* drawing the image on panel and then writing to a file */

            ImageIO.write(dest,"jpeg",new File("dest.jpg"));
        }catch(Exception e){
            e.printStackTrace();
        }
    }

    public BufferedImage convertToGray(BufferedImage src){
        //creating instance and using in-built linear gray scale
        ColorConvertOp grayOp = new ColorConvertOp(
            ColorSpace.getInstance(ColorSpace.CS_GRAY), null);
        return grayOp.filter(src,null);  //converting to gray scale
    }
   
    public static void main (String[] args) {
        JFrame jf=new JFrame("GRAY_SCALE");
        GrayScale obj=new GrayScale();
        jf.getContentPane().add(obj);
        jf.setVisible(true);
        jf.setSize(320,235);
        jf.setDefaultCloseOperation(jf.EXIT_ON_CLOSE);
    }
}
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Reflect or flip an image
Change brightness of image using RescaleOp
Java program to draw partially transparent image using Graphics2D

Today I am going to post a program that will be able to produce all the mColorings of a given graph G.
What is mColoring : The problem statement says that for a given graph G(V,E) and m colors, we have to color all the vertices the graph G with m-colors in all possible ways. This is called m-coloring of a graph G. Suppose for a graph G and 3 colors , we have to show all its 3-colorings.
How to solve the problem : Here we first define a function mColoring(int k) that will use the concept of backtracking. Here in this function we call another function next_color(int k) that will try to color the kth vertex. Now if we are successful then check whether all vertex have been colored. If it is true then we print the solution and then try another solution vector otherwise color the remaining vertex. If we were unsuccessful then we go back (backtrack)) to the last successful situation and try a different path. Our final solution i.e. all the possible m-colorings can be represented as a tree.

Graph G to be colored

Tree for 3-coloring of graph G

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public class MWayGrColor{
    /*G is graph's adjacency matrix and x is solution vector */
    private int G[][],x[],n,m,soln;

    public void mColoring(int k){  //backtracking function
        for(int i=1;i<=n;i++){
           next_color(k);  //coloring kth vertex
           if(x[k]==0)
              return;  //if unsuccessful then backtrack
           if(k==n)  //if all colored then show
              write();
           else
              mColoring(k+1);  /* successful but still left to color */
        }
   }

   private void next_color(int k){
      do{
           int i=1;
         x[k]=(x[k]+1)%(m+1);
         if(x[k]==0)
           return;
         for(i=1;i<=n;i++)
            if(G[i][k]!=0 && x[k]==x[i])  /* checking adjacency and not same color */
               break;
         if(i==n+1)   return;  //new color found
      }while(true);
   }

   private void write(){
      System.out.print("\nColoring(V C) #  "+(++soln)+"-->");
      for(int i=1;i<=n;i++)
          System.out.print("\t("+i+" "+x[i]+")");  //solution vector
   }
   
   public void input(){
         java.util.Scanner sc=new java.util.Scanner(System.in);
         System.out.print("Enter no. of vertices : ");
         n=sc.nextInt();
         G=new int[n+1][n+1];
         x=new int[n+1];
         System.out.print("Enter no. of colors : ");
         m=sc.nextInt();
        System.out.println("Enter adjacency matrix-->");
        for(int i=1;i<=n;i++)
           for(int j=1;j<=n;j++)
               G[i][j]=sc.nextInt();
   }
   
   public static void main (String[] args) {
        MWayGrColor obj=new MWayGrColor();
        obj.input();
        obj.mColoring(1);
        if(obj.soln==0)
           System.out.println("\nNeed more than "+obj.m+" colors");
        else
           System.out.print("\nTOTAL SOLN : "+obj.soln);
   }
}

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