Data Structures in Java

Creating QR Code in Java Data Structures

Through built-in libraries, Java and C# offer a variety of data structures beyond most programming languages In Java, the most common data structures are arrays and linked lists In C#, the NET framework provides a variety of data structures including structures, arrays, collections, dictionaries, queues, and stacks

Unlike Java, C# offers a structure, which acts like a variable that typically holds two or more variables To create a structure, use the struct keyword as follows:

struct name { public datatype variable; };

The name of a structure can be any descriptive name, such as people2get or my_relatives Inside a structure, you must declare one or more variables A typical structure might look like this:

struct MyGrades { public char grade; public int class_number; };

struct geology = MyGrades();

After declaring a variable as a structure, you can store data in the individual fields of a structure like this:

struct geology = MyGrades(); geologygrade = A ; geologyclass_number = 302;

Arrays in Java/C# are known as zero-based arrays, which means that the first element of the array is located at index number 0, the second element of the array is located at index number 1, and so on To create an array in Java, declare its data type and size, such as

datatype [] arrayname = new datatype[arraysize];

The array name can be any descriptive name The array size defines how many items the array can hold To create an array that can hold ten integers, you could define an array like this:

int [] mynumbers = new int[10];

You can create an array and store values in it at the same time by doing the following:

int [] mynumbers = new int[4] {25, 81, 4, 712};

Java and C#

int [] mynumbers = new int[4]; mynumber[0] = 25; mynumber[1] = 81; mynumber[2] = 4; mynumber[3] = 712;

Java offers a linked list class, which simplifies managing a linked list By using a linked list, you can create other data structures, such as stacks and queues To create a linked list, define a variable, such as

LinkedList listname = new LinkedList();

LinkedList <datatype>listname = new LinkedList<datatype>();

To add an item to a linked list, use the add, addFirst, or addLast method with the name of the linked list, such as

LinkedList shopping_list = new LinkedList(); shopping_listadd( Eggs ); shopping_listaddFirst( Milk ); shopping_listaddLast( Bacon );

The first item stored in the linked list would be Milk , followed by Eggs , and Bacon To retrieve data from a linked list, you can use the getFirst, remove, removeFirst, or removeLast method The getFirst method retrieves data only from the linked list whereas the remove, removeFirst, and removeLast methods physically yank that data out of that linked list:

LinkedList shopping_list = new LinkedList(); shopping_listadd( Eggs ); shopping_listaddFirst( Milk ); Systemoutprintln( First = + shopping_listremoveFirst()); Systemoutprintln( First = + shopping_listgetFirst());

The preceding Java code would print the following:

Queue queuename = new Queue(); Stack stackname = new Stack(); Hashtable tablename = new Hashtable();

Each type of data structure uses different methods for adding and removing data A queue uses the Enqueue and Dequeue methods to add and remove data A stack uses the Push and Pop methods to add and remove data A hashtable uses the Add and Remove methods to add and remove data

Both Java and C# are true object-oriented programming languages (unlike C++), so you have no choice but to create and use objects in your programs To create an object, you must define a class stored in its own file A typical class definition looks like this:

class ClassName { datatype propertyname; void methodname() { Commands; } };

The class lists one or more properties and the type of data that property can hold, such as an integer or a floating point number A class also lists one or more method names, which contains code for manipulating an object in some way After you define a class, you can create an object from that class by declaring a variable as a new class type, such as

className objectname = new className();