Ruby to Java

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How to convert from Ruby to Java

Understanding the Basics of Ruby and Java

Ruby and Java are both powerful programming languages, but they differ significantly in syntax and runtime environments. Ruby is known for its simplicity and elegance, while Java emphasizes type safety and performance. Before diving into the conversion process, it’s important to understand the key differences between these languages.

Object-Oriented Paradigm: Classes and Objects

Ruby is an object-oriented language where everything is an object. Java also follows an object-oriented paradigm but is more verbose in its implementation. Let's start a simple class in Ruby and convert it to Java.

Ruby Class Example:

class Person
  attr_accessor :name, :age

  def initialize(name, age)
    @name = name
    @age = age

  def display
    puts "Name: #{@name}, Age: #{@age}"

person ="John", 30)

Java Class Equivalent:

public class Person {
    private String name;
    private int age;

    // Constructor
    public Person(String name, int age) { = name;
        this.age = age;

    // Getters and Setters
    public String getName() {
        return name;

    public void setName(String name) { = name;

    public int getAge() {
        return age;

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

    // Display method
    public void display() {
        System.out.println("Name: " + name + ", Age: " + age);

    public static void main(String[] args) {
        Person person = new Person("John", 30);

Variables and Data Types

Ruby is dynamically typed, meaning variables are bound to objects at runtime. In contrast, Java is statically typed, requiring explicit type definitions.

Ruby Example:

name = "John"
age = 30

Java Equivalent:

String name = "John";
int age = 30;

Methods and Functions

Methods in Ruby are defined using the def keyword and do not require explicit return types. Java methods require a return type and are encapsulated within a class.

Ruby Method:

def greet(name)
  "Hello, #{name}"

puts greet("John")

Java Method:

public class Greeter {
    public static String greet(String name) {
        return "Hello, " + name;

    public static void main(String[] args) {

Control Structures: Conditionals and Loops

Control structures in Ruby are straightforward and user-friendly. Java employs similar structures but requires explicit syntax for defining blocks.

Ruby If-Else:

if age >= 18
  puts "Adult"
  puts "Minor"

Java If-Else:

if (age >= 18) {
} else {

Ruby Loop:

5.times do |i|
  puts i

Java Loop:

for (int i = 0; i < 5; i++) {

Error Handling

Ruby uses exceptions for error handling, and the syntax is quite straightforward. Java also uses exceptions but requires more structure.

Ruby Exception Handling:

  # Code that may raise an exception
  result = 10 / 0
rescue ZeroDivisionError => e
  puts "Error: #{e.message}"

Java Exception Handling:

try {
    // Code that may raise an exception
    int result = 10 / 0;
} catch (ArithmeticException e) {
    System.out.println("Error: " + e.getMessage());


Converting code from Ruby to Java involves understanding the fundamental differences in syntax, typing, and structure. While Ruby's dynamic nature allows for more concise code, Java's static typing and verbosity ensure greater type safety and performance. This guide serves as a starting point for those proficient in Ruby to transition to Java effectively. By keeping these key differences in mind, you can create robust Java applications from your existing Ruby codebase.

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