Collections

Collections are used to store objects and not primitive types. In this task, the goal is to create a collection, and add an element or two to it.

Java

  ArrayList arrayList = new ArrayList();
  arrayList.add(new Integer(0));
  
  /*other features of ArrayList*/
  //define the type in the arraylist, you can substitute a proprietary class in the "<>"
  private ArrayList<int> myarrlist; 
  int i;
  int sum;
  myarrlist = new ArrayList<int>();
  
  //add several values to the arraylist to be summed later
  for(i=0; i<10; i++)
  {
      myarrlist.add(i);
  }

  //loop through myarrlist to sum each entry
  for(i=0; i<myarrlist.size(); i++)
  {
      sum+=myarrlist.get(i);
  }

  //remove the last entry in the ArrayList
  myarrlist.remove(myarrlist.size()-1)

  //clear the ArrayList
  myarrlist.clear();

JavaScript

var array = [];
array.push('abc');
array.push(123);
array.push(new MyClass);
alert( array[2] );

var map = {};
map['foo'] = 'xyz'; //equivalent to: map.foo = 'xyz';
map['bar'] = new MyClass; //equivalent to: map.bar = new MyClass;
map['1x; ~~:-b'] = 'text'; //no equivalent
alert( map['1x; ~~:-b'] );

Objective-C

Compiler: gcc

The NSMutableArray class in Objective C provides a simple, editable array data structure.

NSMutableArray *array = [[NSMutableArray alloc] init];

[array addObject:@"String1"];
[array addObject:@"String2"];
[array insertObject:@"String3" atIndex:1];

NSLog( @"%@, %@, %@", [array lastObject], [array objectAtIndex:0], [array objectAtIndex:1] );
// prints: String2, String1, String3

In perl the value of any variable can be (whats called in perl) a reference to any other simple or complex variable structure, including objects. With hashs (or associative arrays), even the key can be a reference to another variable structure.

my %hash = ( name=>'David', age=>'30' );
my $var = [
  'plain string',
  \%hash,
  [3, 2, 1],
  { City=>'Salt Lake City', State=>'Utah' }
];

$var is a scalar, but its value is an arrayref where the first element is just a string, the second is a hash as defined in %hash, the third is an array, the forth is another hash.

PHP

  $students = array();
  array_push($students, array('name' => 'Joe Smith', 'age' => 21, height=> '72.5', gpa => 3.42 ));

Python

Interpreter: Python 2.5

In Python practically everything is an object, so using any of the provided structures can function as a collection. http://docs.python.org/tut/node7.html

collection = [0, '1'] # Lists are mutable (editable) and can be sorted in place
collection = (0, 1) # Tuples are immutable (not editable)
collection = {0: "zero", 1: "one"} # Dictionaries (Hash)
collection = set([0, '1']) # sets (Hash)

Ruby

Ruby is a 100% object oriented language, so you can use the default Array or Hash structures as collection objects.

Scala

val l = List(1,2,3,4,-1,-2,-4)
l.filter{0<} // get the positive values  List(1,2,3,4)
l.head // 1 -- first element
l.tail // List(2,3,4,-1,-2,-4) -- the rest of the list
l.take(3) // List(1,2,3) -- the first 3 elements in the list
l.drop(4) //  List(-1,-2,-4) -- get rid of the first 4 element in the list
88 :: l.tail //  List(88,2,3,4,-1,-2,-4)
l.take(2) ::: 18 :: l.takeRight(2) //  List(1,2,18,-2,-4)