1 / 9

Arrays

Learn how to create arrays of objects and collections in complex programs. Objects within collections can be accessed individually using the collection-name[index] notation.

rodriguezmarie
Download Presentation

Arrays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Arrays How to create an array of objects

  2. Collections • Writing complex programs using named variables would be impossible • Most objects never yet named. Instead, they are created and placed in collections • Collections are just objects that can hold references to other objects • Objects within collections can be accessed individually • collection-name[index] notation often used

  3. Nature of Object Collection Collection Object Objects in Memory Implication: The objects and collection objects must be created separately

  4. Nature of Value Type Collection Implication: The collection array actually holds the values. For example: int[] myVals = new int[8]; myVals[0]=17; myVals[1]=23; myVals[2]=9; myVals[3]=5; myVals[4]=101; myVals[5]=2; 17 23 9 5 101 2 0 0 Collection Object

  5. Array collection • Collection of specific objects • Object array can hold anything in C# • Defined to be a specific size • Determined upon construction • Can’t be changed • Provides useful properties • [index] to get individual elements (e.g., MyArray[0] is 1st, MyArray[1] is 2nd, etc.) • Length gives number of elements

  6. Declaring Array Basic format: ObjectType[] variableName1 = {element-list}; // Creates collection & elements ObjectType[] variableName2 = new ObjectType[integer-val]; // Creates collection ObjectType[] variableName3; // This array == null until initialized Examples:

  7. Iterating through an Array • Comments: • The Length property returns how many characters there are in an array • i < myData.Length reflects the fact that array coefficients go from 0 to Length-1

  8. Example: Point array in Ism4300 • Comments (based on highlighting): • Yellow: An array member variable is declared • Green: The 9 element collection object is created • Light Blue: The individual objects in the collection are created

  9. Parting words… • In earlier languages (e.g., FORTRAN, C, COBOL), the array was the only built-in collection • Still useful—although the lack of resizing ability is a limitation • Other collection classes—most notably the generic classes—are more flexible • Resizing • Ordering and lookup

More Related