Java 5.0 and ActionScript 3.0 Similarities

I thought there might be some who would like to see the similarities between the Java language and the AS3 language. Enjoy… 

This table was produced by Yakov Fain at:
ActionScript 3.0 - Java5.0 Similarities

Concept/Language Construct Java 5.0 ActionScript 3.0
Class library packaging

.jar

.swc
Inheritance class Employee extends Person{…} class Employee extends Person{…}
Variable declaration and initialization String firstName=”John”;Date shipDate=new Date();int i;int a, b=10;

double salary;

 var firstName:String=”John”;var shipDate:Date=new Date();var i:int;var a:int, b:int=10;

var salary:Number;
Undeclared variables

n/a

 It’s an equivalent to the wild card type notation *. If you declare a variable but do not specify its type, the * type will apply.A default value: undefinedvar myVar:*;
Variable scopes block: declared within curly braces,
  local: declared within a method or a blockmember: declared on the class levelno global variables		 No block scope: the minimal scope is a functionlocal: declared within a functionmember: declared on the class levelIf a variable is declared outside of any function or class definition, it has global scope.
Strings Immutable, store sequences of two-byte Unicode characters Immutable, store sequences of two-byte Unicode characters
Terminating statements with semicolons

A must

 If you write one statement per line you can omit it.
Strict equality operator

n/a

 ===for strict non-equality use!==
Constant qualifier The keyword finalfinal int STATE=”NY”; The keyword constconst STATE:int =”NY”;
Type checking Static (checked at compile time) Dynamic (checked at run-time) and static (it’s so called ‘strict mode’, which is default in Flex Builder)
Type check operator

instanceof

 is – checks data type, i.e. if (myVar is String){…}The is operator is a replacement of older instanceof
The as operator

n/a

 Similar to is operator, but returns not Boolean, but the result of expression:var orderId:String=”123”;var orderIdN:Number=orderId as Number;

trace(orderIdN);//prints 123
Primitives byte, int, long, float, double,short, boolean, char all primitives in ActionScript are objects.Boolean, int, uint, Number, StringThe following lines are equivalent;

var age:int = 25;

var age:int = new int(25);
Complex types

n/a

 Array, Date, Error, Function, RegExp, XML, and XMLList
Array declaration and instantiation int quarterResults[];quarterResults =
new int[4];int quarterResults[]={25,33,56,84};		 var quarterResults:Array
=new Array();orvar quarterResults:Array=[];var quarterResults:Array=
[25, 33, 56, 84];

AS3 also has associative arrays that uses named elements instead of numeric indexes (similar to Hashtable).
The top class in the inheritance tree

Object

Object
Casting syntax: cast the class Object to Person: Person p=(Person) myObject; var p:Person= Person(myObject);orvar p:Person= myObject as Person;
upcasting class Xyz extends Abc{}Abc myObj = new Xyz(); class Xyz extends Abc{}var myObj:Abc=new Xyz();
Un-typed variable

n/a

 var myObject:*var myObject:
packages package com.xyz;class myClass {…} package com.xyz{class myClass{…}}ActionScript packages can include not only classes, but separate functions as well
Class access levels public, private, protectedif none is specified, classes have package access level public, private, protectedif none is specified, classes have internal access level (similar to package access level in Java)
Custom access levels: namespaces

n/a

 Similar to XML namespaces.namespace abc;abc function myCalc(){}

or

abc::myCalc(){}

use namespace abc ;
Console output System.out.println(); // in debug mode onlytrace();
imports import com.abc.*;import com.abc.MyClass; import com.abc.*;import com.abc.MyClass;packages must be imported even if the class names are fully qualified in the code.
Unordered key-value pairs Hashtable, MapHashtable friends = new Hashtable();friends.put(”good”,
“Mary”);friends.put(”best”,
“Bill”);

friends.put(”bad”,
“Masha”);

String bestFriend= friends.get(“best”);

// bestFriend is Bill

 Associative ArraysAllows referencing its elements by names instead of indexes.var friends:Array=new Array();
friends[”good”]=”Mary”;friends[”best”]=”Bill”;

friends[”bad”]=”Masha”;

var bestFriend:String= friends[“best”]

friends.best=”Alex”;

Another syntax:

var car:Object = {make:”Toyota”, model:”Camry”};

trace (car[”make”], car.model);

// Output: Toyota Camry
Hoisting

n/a

 Compiler moves all variable declarations to the top of the function, so you can use a variable name even before it’s been explicitly declared in the code.
Instantiation objects from classes Customer cmr = new Customer();Class cls = Class.forName(“Customer”);Object myObj= cls.newInstance(); var cmr:Customer = new Customer();var cls:Class = flash.util.getClassByName(”Customer”);
var myObj:Object = new cls();
Private classes private class myClass{…} There is no private classes in AS3.
Private constructors Supported. Typical use: singleton classes. Not available. Implementation of private constructors is postponed as they are not the part of the ECMAScript standard yet.To create a Singleton, use public static getInstance(), which sets a private flag instanceExists after the first instantiation. Check this flag in the public constructor, and if instanceExists==true, throw an error.
Class and file names A file can have multiple class declarations, but only one of them can be public, and the file must have the same name as this class. A file can have multiple class declarations, but only one of them can be placed inside the package declaration, and the file must have the same name as this class.
What can be placed in a package Classes and interfaces Classes, interfaces, variables, functions, namespaces, and executable statements.
Dynamic classes (define an object that can be altered at runtime by adding or changing properties and methods).

n/a

 dynamic class Person {var name:String;}//Dynamically add a variable // and a function

var p:Person = new Person();

p.name=”Joe”;

p.age=25;

p.printMe = function () {

trace (p.name, p.age);

}

p.printMe(); // Joe 25
function closures n/a. Closure is a proposed addition to Java 7. myButton.addEventListener(“click”, myMethod); A closure is an object that represents a snapshot of a function with its lexical context (variable’s values, objects in the scope). A function closure can be passed as an argument and executed without being a part of any object
Abstract classes supported n/a
Function overriding supported Supported. You must use the override qualifier
Function overloading supported Not supported.
Interfaces class A implements B{…}interfaces can contain method declarations and final variables. class A implements B{…}interfaces can contain only function declarations.
Exception handling Keywords: try, catch, throw, finally, throwsUncaught exceptions are propagated to the calling method. Keywords: try, catch, throw, finallyA method does not have to declare exceptions.Can throw not only Error objects, but also numbers:throw 25.3;

Flash Player terminates the script in case of uncaught exception.
Regular expressions Supported Supported