Primitive and Abstract Data Types in Java

Primitive data types are the most basic data types available within the Java language. There are 8 types of primitive data types : boolean, byte, char, short, int, long. float and double.

These primitive types have predefined operations in Java type system and no new operations can be defined on them.

Details of primitive data types are as follows:

Category	Types	Size (bits)	Minimum Value	Maximum Value	Precision	Example
Integer	byte	8	-128	127	From +127 to -128	byte b = 65;
	char	16	0	216-1	All Unicode characters	char c = 'A'; char c = 65;
	short	16	-215	215-1	From +32,767 to -32,768	short s = 65;
	int	32	-231	231-1	From +2,147,483,647 to -2,147,483,648	int i = 65;
	long	64	-263	263-1	From +9,223,372,036,854,775,807 to -9,223,372,036,854,775,808	long l = 65L;
Floating-point	float	32	2-149	(2-2-23)·2127	From 3.402,823,5 E+38 to 1.4 E-45	float f = 65f;
	double	64	2-1074	(2-2-52)·21023	From 1.797,693,134,862,315,7 E+308 to 4.9 E-324	double d = 65.55;
Other	boolean	1	--	--	false, true	boolean b = true;
	void	--	--	--	--	--

< and > can be used to compare primitive data types. Comparison using these operators cannot be done for abstract data type like string , list, map.

Abstract data types:

The other type of data type is abstract data type. They are called abstract because their implementation is hidden. The combination of data along with its method is called abstract data type.

In general, there are many possible operations that could be defined for each ADT; however, they often fall into these categories:

1. initialize
2. add data
3. access data
4. remove data

Examples are: List, Stack, Queue, Set, Map, etc.

Object Creation in Javascript

In Javascript, we don't have classes. Instead we use functions. There are two ways to create custom objects.

1. Constructor function
2. Literal Notation

1. Creating an object using constructor function;
        In this method, we first create a function and then create an object using that function.

function Employee(firstName, lastName){
      this.firstName = firstName;
      this.lastName = lastName;

      this.getFullName = function(){
            return this.firstName + " " + this.lastName;
      }
}

var employee = new Employee("Hello","World");

Here, employee is the object and Employee is the constructor function.


2. Literal Notation:

 var employee = {
        firstName : "Hello",
        lastName : "World",
        getFullName : function () {
                      return this.firstName + " " + this.lastName;
        }
}

        document.write("FirstName = " + employee.firstName + "[br/]");
        document.write("LastName = " + employee.lastName + "[br/]");
        document.write("FullName = " + employee.getFullName() ;

In this method, we already have the object. Here, employee is the object name. So, we can access the properties using that object name. Objects created using this method are singletons i.e. any changes to one instance affects the entire script.

Remove duplicate values from array using Javascript

Filter method in JavaScript can be used to easily remove duplicate values from an array in JavaScript.

Syntax:

array1.filter(callbackfn[, thisArg])

Filter method takes two parameters described as below:

Parameter	Definition
array1	Required. An array object.
callbackfn	Required. A function that accepts up to three arguments. The filter method calls the callbackfn function one time for each element in the array.
thisArg	Optional. An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

Return Value

A new array that contains all the values for which the callback function returns true. If the callback function returns false for all elements of array1, the length of the new array is 0.

This property of filter method can be used to remove duplicates from an array.

Code:

var myArray = ["a","b","c","a"];

var newArray = myArray.filter(function(vale,index,array){

  return array.indexOf(value)==index;

});

alert(newArray);

indexOf(value) returns the first index of value. If it is not equal to the current value, filter returns false, so the value is not included in newArray. Thus, newArray will have unique values only.