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So we’ve seen lots of examples of our Fibonacci program in scripting languages, but other than C, I haven’t touched on many compiled languages. So here is a version in Java, probably one of the most common and popular languages in use today. Considered by advocates to be the among the best enterprise application development languages, we’ll see here how to write our simple program.

/*
 * Much like C’s stdio.h, the java.io.* classes will let us access stdin and stdout.
 */

import java.io.*;

/*
 * Like Ruby, in java, everything is an object. To write a program, you’ll need to
 * start by declaring a class. As in C, our program execution starts with the main
 * function. Also like C, Java is a compiled language, so you’ll need to compile 
 * the code and then run the class using the java interpreter.
 */

class Fibonacci {

  /*
   * So here we are defining the main function. Remember that this is supposed to
   * actually run this program, so the function needs to be `public`, in addition,
   * it’s `static`, meaning we can call this method without an object of the Fibonacci
   * class being instantiated, and it doesn’t need to return anything, as it will
   * run by the interpreter, which will handle the exit status. 
   */

  public static void main(String args[]) {

    /* 
     * We are using System.out.println here, but newer versions of Java have the printf method.
     */

    System.out.println("How many numbers of the sequence would you like?");

    /*
     * I’m sure there’s more than one way to skin a cat, but to read stdin here, we
     * are creating a new BufferedReader, which will read one line of input.
     */

    InputStreamReader sr = new InputStreamReader(System.in);
    BufferedReader br    = new BufferedReader(sr);

    /*
     * Now here is a concept we haven’t addressed yet. The java compiler complains if
     * you try to call a method that could throw an exception (error), so I’ve included
     * an example here of how to handle the exceptions that could be thrown. Also, like
     * in our previous examples, we are casting the input to an integer.
     */

    try {
      String input = br.readLine();
      int n = Integer.valueOf(input).intValue();
      fibonacci(n);
    } catch (NumberFormatException e){
      System.out.println("That is not an integer. Please enter an integer value");
    } catch (IOException e) {
      System.out.println("I did not recieve an input");
    }
  }

  /*
   * So here is our Fibonacci function. like the main function, it is public and can be
   * called without creating a Fibonacci object. We’ve also introduced a new method of 
   * calculating the sequence without using a temporary variable. In a later post, I will
   * examine the different algorithms used to calculate the Fibonacci sequence, and compare
   * performance in multiple languages.
   */

  public static void fibonacci(int n){
    int a=0,b=1;

    for (int i=0;i<n;i++){
      System.out.println(a);
      a=a+b;
      b=a-b;
    }
  }
}

HTML code generated by vim-color-improved v.0.3.2.Download this code: fibonacci.java

This entry was posted on Sunday, January 6th, 2008 at 11:53 am and is filed under Fibonacci Project. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.