Approach to Java Programming

What is Java?

Java is a high level programming language, which is developed by Sun Micro-systems and released in 1995.

Java is a object oriented programming language which consists of classes and objects.

Java is a platform independent language which helps to write once and run wherever.

Environment Setup

Download Java compiler:

Install the downloaded file.

Adding Environment Variable

  Go to Control Panel:

Check whether Java installed properly from command line.

Set and save the notepad file in proper path

While executing we have to go to complete path call file.

Compiling a Java program from command line

Running a Java Program from command line

Writing a Basic Java Program

 Step1: Write Program in Notepad and save in specified folder to identify. The class name and file name should same.

 Step2: Compile  the program

Step3: Run the program 

Variable Declaration

• Variable is a memory pointer declared to store some value.
• It can be any name given but should not exceed 32 charecters.
• Should start with character or underscore(_).

   Syntax: Datatype Variable_Name;

Defining a Class 

   Class is a blue print and logical representation of object.

  Object is a physical representation of class. Takes all the members from class.

   Syntax to define class:   Class Class_Name
                                         {
                                               // Class members
                                         }

Constructor

Declaring an Object   Syntax to define object: Class_Name object_name= new Class_Name();

   Program to specify usage of Class and Object.   

Accessing Instance Variables and Methods

Conditional Statements

1.   if() statement:

2.  Switch() statement:

Looping Statements

Looping statements are used to iterate a block of statements until a specified condition becomes true.

Looping statements are : for(), while(), dowhile(), goto(). 

Iteration is an execution of block of statements for one time. When a sequence of instructions is executed in a repeated manner until condition becomes false, it is called a loop.

1.   for() loop:

 For statement is used whenever the number of iterations are fixed or known.

 Syntax: for(expression1;expression1;expression1)

             {

                       //block of statements

             }

2.   While() loop:

Syntax: While(Condition)

             {

                       //block of statements

             }

String Manipulation

   1. Reading and displaying a string

    

2. String Concatenation

  

   

3. Length of a String ( length() function):

3. Searching a String ( indexOf() function):

  

4. Substrings ( substring() ):

    Substring is a string function used to search and return a string based on index.

   Syntax: string.substring( Starting_index, Ending_index)

   

File Handling

  Example to Parse Menu

  Program:

  File Input Given

  Output

  Output Generated