From dictionary.reference.com:
Computers. to analyze (a string of characters) in order to associate groups of characters with the syntactic units of the underlying grammar.
The context of the definition is the translation of program text or a language in the general sense into its component parts with respect to a defined grammar -- turning program text into code. In the context of a particular language keyword, though, it generally means to convert the string value of a fundamental data type into an internal representation of that data type. For example, the string "10" becomes the number (integer) 10.
Parsing is the division of text in to a set of parts or tokens.
Parsing is to read the value of one object to convert it to another type. For example you may have a string with a value of "10". Internally that string contains the Unicode characters '1' and '0' not the actual number 10. The method Integer.parseInt takes that string value and returns a real number.
String tenString = "10"
//This won't work since you can't add an integer and a string
Integer result = 20 + tenString;
//This will set result to 30
Integer result = 20 + Integer.parseInt(tenString);
Parsing means we are analyzing an object specifically. For example, when we enter some keywords in a search engine, they parse the keywords and give back results by searching for each word. So it is basically taking a string from the file and processing it to extract the information we want.
Example of parsing using indexOf to calculate the position of a string in another string:
String s="What a Beautiful day!";
int i=s.indexOf("day");//value of i would be 17
int j=s.indexOf("be");//value of j would be -1
int k=s.indexOf("ea");//value of k would be 8
paresInt essentially converts a String to a Integer.
String s="9876543";
int a=new Integer(s);//uses constructor
System.out.println("Constructor method: " + a);
a=Integer.parseInt(s);//uses parseInt() method
System.out.println("parseInt() method: " + a);
Output:
Constructor method: 9876543 parseInt() method: 9876543
Parsing can be considered as a synonym of "Breaking down into small pieces" and then analysing what is there or using it in a modified way. In Java, Strings are parsed into Decimal, Octal, Binary, Hexadecimal, etc. It is done if your application is taking input from the user in the form of string but somewhere in your application you want to use that input in the form of an integer or of double type. It is not same as type casting. For type casting the types used should be compatible in order to caste but nothing such in parsing.
Parsing is just process of analyse the string of character and find the tokens from that string and parser is a component of interpreter and compiler.It uses lexical analysis and then syntactic analysis.It parse it and then compile this code after this whole process of compilation.
You could say that parsing a string of characters is analyzing this string to find tokens, or items and then create a structure from the result.
In your example, calling Integer.parseInt on a string is parsing this string to find an integer.
So, if you have:
String someString = "123";
And then you invoke:
int i = Integer.parseInt( someString );
You're telling java to analyze the "123" string and find an integer there.
Other example:
One of the actions the java compiler does, when it compiles your source code is to "parse" your .java file and create tokens that match the java grammar.
When you fail to write the source code properly ( for instance forget to add a ; at the end of a statement ), it is the parser who identifies the error.
Here's more information: http://en.wikipedia.org/wiki/Parse
Source: Stackoverflow.com