programmer.java

import java.util.*;

class Programmer {
  private String name;
  private int age;
  private List<String> languages;

  public Programmer(String name) {
    this.name = name;
    this.languages = new ArrayList<String>();
  }

  public void learn(String languages) {
    this.languages.add(languages);
  }

  public String getName() {
    return name;
  }

  public void setAge(int age) {
    this.age = age;
  }

  public int getAge() {
    return age;
  }

  public String toString() {
    return "A programmer named " + name
      + ", " + age + " years old, knows " + languagesString() + ".";
  }

  private String languagesString() {
    String result = Arrays.toString(languages.toArray());
    return result.substring(1, result.length() - 1);
  }

  public static void main(String[] args) {
    Programmer alice = new Programmer("Alice");
    alice.setAge(8);
    String[] languages = { "Java", "Ruby", "Python" };

    for(int i = 0; i < languages.length; i++) {
      alice.learn(languages[i]);
    }
    System.out.println(alice);
  }
}

programmer.rb

class Programmer                      # No braces, use `end` instead
  attr_accessor :age                  # Symbol, Getter+Setter
  attr_reader :name                   # Getter

  def initialize name                 # Define method, Constructor, Optional parentheses
    @name = name                      # Instance variable
    @languages = []                   # Array
  end

  def learn language
    @languages << language            # invoking method array<<
  end

  def to_s                            # toString, No return data type
    "A programmer named #{name}, #{age} years old, knows #{languages_string}."
  end                                 # String interpolation, Optional parentheses

  private

  def languages_string
    @languages.join(", ")             # Implicit return
  end
end

alice = Programmer.new('Alice')       # Object initialization
alice.age = 8                         # Invoking method age=

languages = %w{Java Ruby Python}      # Alternative array instantiation with perl % syntax
languages.each do |language|          # Iterate over an array
  alice.learn language
end

puts alice                            # Output