4. Basic terms
Object - Objects have states and behaviors.
Class - A class can be defined as a blue print that
describe the behaviors/states that object.
Methods - A method is basically a behavior.
Instance Variables - States of an objects, each
object has its unique set of instance variables.
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5. Keep in Mind
Case Sensitivity - Hello and hello would have
different meaning in Java.
Class Names - For all class names the first letter should
be in Upper Case.
Example : class MyFirstJavaClass
Method Names - All method names should start with a
Lower Case letter and each inner word's first letter
should be in Upper Case.
Example : public void myMethodName()
Program File Name - Name of the program file should
exactly match the class name.
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6. Simple Program
class HelloWorldApp {
public static void main(String[] args) {
HelloWorldApp hello = new HelloWorldApp();
hello.sayHello();
}
public void sayHello(){
System.out.println(“Hello”);
}
}
O/P : Hello
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7. Modifiers and Variables
Access Modifiers :
default, public , protected, private
Non-access Modifiers :
final, abstract, static, strictfp, synchronized and volatile
Type of variables in Java:
Local Variables
Class Variables (Static Variables)
Instance Variables (Non static variables)
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8. public static void main ?
java program processing starts from the main()
method.
Public ?
Static?
Void?
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9. Object Oriented Principles
Abstraction
Hiding the implementation (abstract class and interface)
Encapsulation
Wrapping up of data into single unit. (data hiding)
Inheritance
Reusable the properties of existing class
Polymorphism
Overloading and Overriding
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10. Thread
Create Thread by implements Runnable interface or
extends Thread class
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11. Exception Handling
Problem that
arises during the
execution of a
program.
try{}
catch{}
finally{}
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12. Some important concepts
Constructor
Package
Multithreading
Synchronized
This keyword
finally
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