Tuesday, May 6, 2014

Arrays and Indexers in JRuby



Today's post is about Arrays and Indexers in JRuby. Here below you will find a very easy to follow program, that demonstrate arrays and indexer, by implementing some simple tasks that will make you grasp the idea of those 2 features real quick. The main goal of this post, is not really teaching arrays because, come on, you probably already know "all" about them, in fact, it is more to show you how you do that in JRuby, in this case, compared to all other 22 languages on future posts, which essentially, is the real aim behind this blog.

This is the first post on this series on a language targeting the JVM. Besides the fact that I had the code from a previous post written in (Iron)Ruby, the newly released version of the (J)Ruby plugin for NetBeans IDE (http://plugins.netbeans.org/plugin/38549/?show=true) helped me decide what to publish next.

By the way, if you missed my most recent post, "New Series - Arrays and Indexers", check it out. It has more details about the following program, and a bunch of definitions for the concepts used on this, and the following, posts.

I encourage you to copy the code below and try it yourself, normally, all programs you find in this blog are source code complete, just paste it on your IDE and run it.

There is room for improvement of the code, using generics is one example, but Generics, Collections, lambdas, etc. will have their own "series" of posts.


require "java"

# Console Program  
def main()  
    # Single-dimensional Array(s)  
    print_title("Reverse Array Elements")  
   
    # Declare and Initialize Array of Chars        
    letters = Array.new(5," ")  
    letters[0] = "A"  
    letters[1] = "E"  
    letters[2] = "I"  
    letters[3] = "O"  
    letters[4] = "U"  
   
    print_array(letters)    
    inverse_letters = reverse_char(letters)  
    print_array(inverse_letters)  
  
    print_title("Sort Integer Array Elements")  
    # Declare and Initialize Array of Integers     
    numbers = [10, 8, 3, 1, 5]  
      
    print_array(numbers)         
    ordered_numbers = bubblesort(numbers)     
    print_array(ordered_numbers)  
  
    print_title("Sort String Array Elements")    
   
    # Declare and Initialize and Array of Strings   
    #names = Array.new(5, ["Damian","Rogelio","Carlos","Luis","Daniel"])  
    # or just   
    names = ["Damian",   
      "Rogelio",   
      "Carlos",   
      "Luis",   
      "Daniel"]  
  
    print_array(names)     
    ordered_names = bubblesort(names)     
    print_array(ordered_names)  
  
    # Multi-dimensional Array (Matrix row,column)     
    print_title("Transpose Matrix")     
  
    # for an empty table initialized to 0s  
    # matrix = Array.new(rows,0) { Array.new(cols,0) }  
    matrix = [[6, 4, 24],        
              [1, -9, 8]]  
  
    print_matrix(matrix)  
    transposed_matrix = transpose_matrix(matrix)     
    print_matrix(transposed_matrix)    
   
    # Jagged Array (Array-of-Arrays)     
    print_title("Upper Case Random Array & Graph Number of Elements")     
  
=begin  
# Creating an array of string arrays using the String.Split method     
# instead of initializing it manually as follows:     
#   
# text = [      
#  [ ["word1", "word2, "wordN"],      
#  [ ["word1", "word2, "wordN"],      
#  ...  
#  ]     
#       
# Text extract from: "El ingenioso hidalgo don Quijote de la Mancha"          
=end  
    text = [  
    "Hoy es el dia mas hermoso de nuestra vida, querido Sancho;".split(" "),      
    "los obstaculos mas grandes, nuestras propias indecisiones;".split(" "),      
    "nuestro enemigo mas fuerte, miedo al poderoso y nosotros mismos;".split(" "),      
    "la cosa mas facil, equivocarnos;".split(" "),      
    "la mas destructiva, la mentira y el egoismo;".split(" "),      
    "la peor derrota, el desaliento;".split(" "),      
    "los defectos mas peligrosos, la soberbia y el rencor;".split(" "),      
    "las sensaciones mas gratas, la buena conciencia...".split(" ")  
    ]   
   
    print_jagged_array(text)     
    uppercase_random_array(text)        
    print_jagged_array(text)     
    graph_jagged_array(text)  
  
    # Array Exceptions  
    print_title('Common Array Exceptions')  
      
    print_common_array_exceptions(nil)  
    print_common_array_exceptions(text)    
  
    # Accessing Class Array Elements through Indexer  
    print_title('Alphabets')  
      
    vowels = Alphabet.new(5)  
    vowels[0] = "a"  
    vowels[1] = "e"  
    vowels[2] = "i"  
    vowels[3] = "o"  
    vowels[4] = "u"  
  
    puts "\nVowels={%s}" % [vowels[0],vowels[1],vowels[2],vowels[3],vowels[4]].join(",")  
  
    en = Alphabet.new("abcdefghijklmnopqrstuvwxyz")     
  
    puts "English Alphabet = {%s}" % [en]  
  
    puts "Alphabet Extract en[9..19] = {%s}" % [Alphabet.new(en.slice(9, 10))]  
  
    word1 = [en[6],en[14],en[14],en[3]].join("")  
    word2 = [en[1],en[24],en[4]].join("")     
    word3 = [en[4],en[21],en[4],en[17],en[24],en[14],en[13],en[4]].join("")     
    puts "\n%s %s, %s!\n" % [word1, word2, word3]  
   
    gets  
end  
  
def reverse_char(arr)  
    arr.reverse  
end   
  
def bubblesort(arr)    
    for i in arr.reverse  
        for j in (0..arr.count-2)  
            if arr[j] > arr[j + 1]      
                swap = arr[j]     
                arr[j] = arr[j + 1]     
                arr[j + 1] = swap     
            end      
        end   
    end     
    arr  
end  
  
def transpose_matrix(m)    
=begin  
# Transposing a Matrix 2,3    
#       
#   A =  [6  4 24]T [ 6  1]    
#        [1 -9  8]  [ 4 -9]    
#                [24  8]    
=end  
    transposed = Array.new(m[0].size) { Array.new(m.size) }   
    for i in 0..(m.size-1)     
        for j in 0..(m[0].size-1)     
            transposed[j][i] = m[i][j]  
        end  
    end  
    transposed    
end  
  
def uppercase_random_array(arr)        
    r = java.util.Random.new()
    i = r.nextInt(arr.size)
    for j in 0..(arr[i].size-1)     
        arr[i][j] = arr[i][j].upcase  
    end  
end  
  
def print_array(arr)  
    puts "\nPrint Array Content #{arr.class.name}[#{arr.size}]"  
    for i in 0..(arr.size-1)  
        puts " array [%2s] = %2s" % [i, arr[i]]  
    end  
end  
  
def print_matrix(m)  
    puts "\nPrint Array Content #{m.class.name}[#{m.size}][#{m[0].size}]"  
    for i in 0..(m.size-1)  
        for j in 0..(m[0].size-1)  
            puts " array [%2s,%2s] = %2s" % [i, j, m[i][j]]  
        end  
    end  
    m  
end  
  
def graph_jagged_array(arr)  
=begin  
# When using Arrays, we can use for(each) instead of for by index  
#    for s in arr    
#        for w in s   
#        end  
#    end  
=end   
    puts "\nPrint Text Content #{arr.class.name}"  
    for i in 0..(arr.size-1)    
        line = ""  
        line += "Line %2s|" % (i+1).to_s   
        for j in 0..(arr[i].size-1)     
            line += " * "  
        end              
        line += "(#{arr[i].size})"  
        puts line  
    end  
end  
  
def print_jagged_array(arr)  
    puts "\nPrint Jagged Array Content #{arr.class.name}"  
    for i in 0..(arr.size-1)  
        line = ""  
        for j in 0..(arr[i].size-1)       
            line += " " + arr[i][j]  
        end  
        if line == line.upcase  
            line += " <-- [UPPERCASED]"  
        end  
        puts line  
    end  
end  
  
def print_common_array_exceptions(arr)  
    begin    
        arr.fetch(100)  
    rescue Exception => ex  
      puts "\nException: \n%s\n%s" % [ex.class.name, ex.message]  
    #else  
    #   others  
    end  
end  
  
def print_title(message)     
    puts ""    
    puts ("=" * 54)     
    puts message     
    puts ("=" * 54)  
end       
  
  
class Alphabet  
    # Array Field     
    @letters = []  
  
    # Indexer Get/Set Property  
    def [](idx)  
        @letters[idx]  
    end  
    def []=(idx, value)  
        @letters[idx] = value.upcase  
    end  
      
    # Read-Only Getter  
    def length  
        @letters.size  
    end            
  
    # Constructor/Initializer  
    def initialize(param)    
        if param.class == 1.class  
            @letters = Array.new(param, " ")  
        elsif param.class == "".class  
            @letters = param.upcase.chars.to_a  
        elsif param.class == [].class  
            @letters = param  
        else  
            @letters = nil  
        end  
    end  
  
    # Overridden Method      
    def to_s  
        @letters.join(",")  
    end  
   
    # Method     
    def slice(start, length)  
        @letters[start..start+length-1]  
    end  
  
end  
  
main


The output:



































VoilĂ , that's it. Next post in the following days.

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