Intro to Java for Ruby Developers

1. Intro to

2. Intro to Me

3. Plan of Attack
 History and Impact of Java
 Characteristics of Java
 Development and Compilation in Java
 Installing IDE
 Similarities with Ruby
 Differences with Ruby
 Objects, Variables, Classes, Constructors, Methods, Exception Handling,
Multiple Inheritance
 Examples

4. History and Impact of Java

5. History and Impact of Java
 Created by Sun Microsystems in 1995
 Largely derived and simplified from C++
 “Write once, run anywhere”
 Amazon, Facebook, Google, Square, Twitter
 https://blog.twitter.com/2011/twitter-search-now-3x-faster

6. Characteristics of Java
 Simple
 Object-oriented
 Interpreted
 Multithreaded
 Dynamic
Reference:
http://docs.oracle.com/javase/tutorial/getStarted/intro/definition.html
 Architecture neutral
 Portable
 High performance
 Robust
 Secure

7. Development
Java Development Kit
Java Runtime
Environment
Java Virtual Machine
Reference: http://www.javabeat.net/what-is-the-difference-between-
jrejvm-and-jdk/

8. Compilation
Reference:
http://docs.oracle.com/javase/tutorial/getStarted/intro/definition.html

9. Installation
 Install Java
 http://support.apple.com/kb/DL1572
 Install JDK
 http://www.oracle.com/technetwork/java/javase/downloa
ds/jdk8-downloads-2133151.html
 Install IntelliJ
 https://www.jetbrains.com/idea/download/

10. Similarities with Ruby
 Object-oriented
 Provide inheritance
 A class may extend only one other class
 Public, private, protected modifiers
 Automatic garbage collection

11. Objects
 Ruby
 Everything is an object, including classes and instances of
types
 Java
 Primitive data types – do not extend object class
 int, double, boolean, char, etc.
 Strings have special support from java.lang.String
class
 Immutable
 Technically not a primitive data type

12. Variables
Ruby
age = 2
age = “two”
Java
int age = 2;
String age = “two”;

13. Classes
Ruby
class Dog
end
d = Dog.new
Java
public class Dog(){
}
Dog d = new Dog();

14. Constructors
 Ruby uses the “initialize” keyword for all classes
class Dog
def initialize(breed)
@breed = breed
end
end
 Java requires the public keyword and class name
public class Dog(){
public Dog(String breed){
this.breed = breed;
}
}

15. Methods
Ruby
def getAge
return 1
end
Java
public int getAge(){
return 1;
}

16. Naming Conventions
 Packages
 Lowercase i.e. com.mycompany.util.package
 Classes
 CamelCase
 Interfaces
 CamelCase
 Starts with an “I” to denote interface (not required)
 Methods, Variables
 mixedCase
 Constants
 All caps

17. Quick Example

18. Exception Handling
Ruby
begin
rescue Exception1
rescue Exception2
ensure
end
Java
try {
}
catch (Exception e) {
}
finally() {
}

19. Multiple Inheritance
 Ruby uses modules and mixins
 Java uses interfaces that consist of abstract methods

20. Let’s get to it!