Collections

Programming basics

A collection — sometimes called a container — is simply an object that groups multiple elements into a single unit. Collections are used to store, retrieve, manipulate, and communicate aggregate data. Typically, they represent data items that form a natural group, such as a poker hand (a collection of cards), a mail folder (a collection of letters), or a telephone directory (a mapping of names to phone numbers). If you have used the Java programming language — or just about any other programming language — you are already familiar with collections.

Collection methods

Collection methods in Pseudocode are:

• .addItem( new data item )
• .resetNext( ) start at beginning of list
• .hasNext( ) checks whether there are still more items in the list
• .getNext( ) retrieve the next item in the list
• .isEmpty( ) check whether the list is empty

Write, in pseudocode, a collection that adds the first names of everyone in the class. You then must find the name of everyone whose name starts with M.

Standards

• Describe the characteristics and applications of a collection.
• Construct algorithms using the access methods of a collection.
• Discuss the need for sub-programmes and collections within programmed solutions.
• Construct algorithms using pre-defined sub-programmes, one-dimensional arrays and/or collections.

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