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  Combination in Java

 Purpose

This is the Java version of our combination application.

 Requirements

You need Epoc Java SDK (see tools section).

 Source code

Below is the .java file. For .aif, .app, .lst, .mbm, .rss, .txt and .jar, please download the ZIP file.

/*
 * Combination.java
 * Java
 */


package samples;


/**
 * A sample that computes factorial(n) and combination(n,p)
 */
public class Combination
{
    private int myN, myP;

    public Combination(int n, int p)
    {
        myN = n;
        myP = p;
    }


    public long factorial(int n)
    {
        return (n <= 1) ? 1 : n*factorial(n-1); // he-he... let's mix a ternary operator (?) and recursion...
    }

    public long combination(int n, int p)
    {
        return factorial(n) / (factorial(n - p) * factorial(p));
    }

    public void go()
    {
        System.out.println("Combination>Java");
        System.out.println();
        System.out.println("factorial(" + myN + ") = " + factorial(myN));
        System.out.println("factorial(" + myP + ") = " + factorial(myP));
        System.out.println("factorial(" + (myN-myP) + ") = " + factorial(myN-myP));
        System.out.println("combination(" + myN + "," + myP + ") = " + combination(myN, myP));
    }

    public static void main(String[] args)
    {
        if (args.length != 2)
        {
            System.err.println("Usage: Combination n p");
            System.exit(0);
        }

        int argN = java.lang.Integer.parseInt(args[0]),
            argP = java.lang.Integer.parseInt(args[1]);

        Combination comb = new Combination(argN, argP);
        comb.go();
    }
}

Here's the .txt file that contains arguments to fire the JVM (classpath, class name and class args):

-cp combination.jar samples.Combination 7 4

Here's the .lst file used by bmconv to generate the .mbm (Multi-bitmap) from the collection of .bmp: (Combination16i.bmp is the 16x16 icon, Combination16m.bmp is the transparency mask to apply to the same icon for drawing, Combination24i.bmp is the 24x24 icon, etc):

Combination.mbm

/c4Combination16i.bmp
Combination16m.bmp
/c4Combination24i.bmp
Combination24m.bmp
/c4Combination32i.bmp
Combination32m.bmp
/c4Combination48i.bmp
Combination48m.bmp

And here's the .rss to generate the .aif with aiftool! (Phew...)

// Combination.rss
// Epoc
// Java
#include <aiftool.rh>

RESOURCE AIF_DATA
    {
    app_uid=0x01234567;
    //
    caption_list=
        {
        CAPTION { code=ELangEnglish; caption="Combination"; },
        CAPTION { code=ELangFrench; caption="Combinaison"; },
        CAPTION { code=ELangGerman; caption="Kombination"; },
        CAPTION { code=ELangSpanish; caption="Combinación"; }
        };
    //
    num_icons=4;
    //
    embeddability=KAppNotEmbeddable;
    }

 Comments

See the magic of Java:

  1. We are using exactly the same Java source code as for other platforms
  2. Same remark for the byte-code! Not even a single recompilation!!!
  3. You may install the byte code (along with its accompanying files) either on WINS emulator or on a real device. No need to specify target machine when you compile Java code :)

The core functions are located at the top of the .java file: factorial(), combination() and go(). Be careful, there's also Combination() with capital 'C', but its the constructor!

Here, note that the amount of overhead is about the same as for the C++ version for Epoc.

Install the .jar (jarred-up class), .aif (Application Information File), .app (Links app to its UID), .txt (used to fire the JVM with the right arguments and the right class).

For your convenience, I added some more files in case you need more info on how to build the whole stuff:

  • The make-aif.bat generates the .mbm and .aif
  • The collection of .bmp to generate the .mbm

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