Computer Science Java

Enclosing data within a class and hiding the details of the its implementation.

Setting classes, methods, and variables to private

• Private classes, methods, and variables cannot be accessed and changed outside of the class.
• Public classes, methods, and variables can be accessed and changed as long as they are not final.

When 2 methods have the same name but different numbers and parameter types.

When something has no references to it, Java releases its memory back to the operating system. Java does it automatically.

Statement of conditions that have to be true before a client executes a method.

Describes the value returned by a method. Void methods describe any changes made to the calling object.

How easy a program is can be understood

• Meaningful variable names
• Space between lines of code
• Commenting the code
• Indenting blocks of code
• Using named constants

So a programmer reading your code can understand it

You can use the same syntax and similar operations for different data types

Creating one uses the diamond notation <>

You put the type into the diamond

Primitive types are not allowed; the data types have to be wrapper classes

An interface is a shell that contains the public methods for a class

It contains only the method headers; it does not contain any actual code

An interface can be reused by simply writing a new implementation

An ADT is a specific set of data and what the data does while a data structure is the programming or implementation of that data.

An array and a linked list are examples of data structures

A bag is an example of an ADT

• Add an item
• +add(newEntry: T): boolean

• Remove an item
• +remove(): T
• +remove(anEntry: T): Boolean or +remove(anEntry: T): T

Test if there is room to add a new item (Test if the data structure is full)

• Test if the data structure is empty
• +isEmpty(): boolean

• Count how many items are in the data structure
• +getCurrentSize(): integer

• Test if a particular item is in the data structure
• +contains(anEntry: T): boolean

• Determine how many of a particular item are in the data structure
• +getfrequencyOf(anEntry: T): integer

Print a list of all the items in the data structure

• Convert the data structure to an array
• +toArray(): T[]

It’s a way to pictorially describe the attributes and the methods of a class

It’s a box with three parts, the name, the attributes, and the methods of the class

It uses + for public items, - for private items

Javadoc is a standard way of documenting Java programs

It creates an HTML document containing a summary of the methods

All Javadoc items are comments

All Javadoc descriptions starts with /**

• /** Adds a new entry to this bag.    
• @param newEntry The object to be added as a new entry.
• @return True if the addition is successful, or false if not. */

• /** Adds a new entry to this bag.    
• @param newEntry The object to be added as a new entry.
• @return True if the addition is successful, or false if not. */

Data structure that uses multiple arrays to represent an array of records

They are easy to create and use

The danger is that they are connected only in the programmer’s mind

A group of data items that are all the same type

An array is an easy-to-use data structure

It has a fixed size and cannot grow or shrink.  For this reason, it is usually very wasteful of memory

ArrayLists

• Allows dynamically sized arrays
• This means the arrays can grow and shrink as needed
• Locations can be inserted or deleted as desired

• It is easy to add and remove items form the data structure
• Order of putting items into the data structure doesn't matter
• You wont take them out in the order you put them in
• You can put two of the same thing into the data structure
• You can check if an item is in the data structure

• A collection of items that are linked together
• The items in the list are called nodes
• Each node points to the next node
• There is a pointer to the first node in the list
• There is no such (physical) thing as a linked list in a program.  It’s only in memory.

• Assigning memory to a new object.
• Instantiating a node

• currentNode = firstNode;
•    while (currentNode != null)
•       {
•           currentNode = currentNode.next;
•       }

Describes the data and behavior associated with instances of that class

Group of statements that execute an operation

Containers that store values

Executes a set of instructions when a condition is met