Chapter 6                      

Classes & Objects in Java


⦁ Class is a description of an object's property and behavior.
⦁ Creating class is as good as creating data type.
⦁ Class is defining a category of data.


Object
⦁ It is a real world entity.
⦁ It is an instance of a class.
⦁ It consumes memory to hold property.


Steps for creating an object
⦁ Step 1 : DemoClass newObject ; 
Here newObject is an variable of DemoClass.
⦁ Step 2 : newObject = new DemoClass ;
Here the variable is initialized with an object of DemoClass.


Comments

Post a Comment

Popular posts from this blog

Image
Chapter 2        Compilation and Execution of a Java Program ⦁ Java Language uses only one compiler javac.exe for all platforms. ⦁ After compilation of a java program every class in source code will convert into individual Byte code. ⦁ A Byte code can be execute on any operating system with help of Java Virtual Machine (JVM). ⦁ JVM consists an Interpreter (which is  Just-in-time compiler) can can convert Byte code into operating system readable form. ⦁ JVM differs fro compiler to compiler. ⦁ Java Developer Kit (Jdk) contains tools needed to develop the java program like compiler (javac.exe), Application Launcher (java.exe), etc. ⦁ Java Runtime Environment (Jre) contains JVM and Java package Classes (Java library). ⦁ Code for compilation a java program on command prompt : javac FileName.java ⦁ Code for execution of java program on command prompt : java FileName
Read more
Chapter 5                     Type conversion in Java The process through which we convert value of one data type into another data type is called as Type Conversion. ⦁ If we want to store a value of lower size data type value into higher size data type variable  e.g. float a=3; it is permissible in java language. this type of the conversion is called widening conversion. ⦁ We cannot directly assign a higher size data type variable e.g. int a=3.5; //error syntax to assign higher size data type value into lower size data type variable                                             HigherSizeDatatype variable=(lowersizedat type) value ; e.g. int a=(int)3.5; ⦁ It will assign integer part of 3.5 which is 3 to a.    
Read more
Chapter 3        First Program in Java ⦁ Syntax for deceleration of class access specifier class ClassName { /* Body of class is followed by curly bracket*/ } ⦁ An outer class can be followed by either public access specifier or default access specifier. ⦁ Name of class and name of source code must be same. ⦁ The main() function must follow the following prototype : public static void main (String [] args) { // Body of main() function } ⦁ Code of HelloWorld.java class HelloWorld { public static void main (String [] args) { System.out.println("Hello World"); } } Comments :- a. Here System is a predefined class. b. out is a static member reference variable of System class which contains address of an variable of PrintStream class. c. println() is a member function of PrintStream class. Output :- Hello World ⦁ We have to write an access specifier with every member in a class.
Read more