Core java lessons
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This document provides an overview of core Java concepts including object-oriented programming (OOP) principles like classes, objects, encapsulation, abstraction, inheritance, and polymorphism. It also discusses Java language benefits like being simple, portable, robust, and suitable for distributed environments. Finally, it outlines how to set up a Java development environment and write a basic "Hello World" program to get started with Java programming.
Core java lessons
- 1. CORE JAVA LESSONS WRITE ONCE RUN ANYWHERE [email protected]
- 2. OOPS Concept Think, walk and live in Object oriented paradigm
- 3. OOPS Concept Classes and Objects Encapsulation Abstraction Inheritance Polymorphism
- 4. OOPS Concept – Classes and Object Class - A class can be defined as a template/blue print that describes the behaviours/states that object of its type support. Object - Objects have states and behaviours/states . Example: A dog has states - color, name, breed as well as behaviors -wagging, barking, eating. An object is an instance of a class.
- 5. OOPS Concept – Encapsulation Class A Private Data Operations Class B Private Data Operations • Encapsulation is the mechanism that binds together code and the data if manipulates, and keeps both safe from outside interference and misuse. • One way to think about encapsulation is as a protective wrapper that prevents the code and data from being arbitrarily accessed by other code defined outside the wrapper.
- 6. OOPS Concept – Abstraction • Abstraction refers to the act of representing essential features without including the background details. • hiding unnecessary data from the users and making the application as user friendly then it is called as abstrcation Data abstraction is a technique of creating new data types that are well suited to an application It allows creation of user defined data types, having the properties of built in data types and set of permitted operations
- 7. OOPS Concept – Inheritance • Inheritance is the property which allows a Child class to inherit some properties from its parent class. • New Data types can be defined as extension to previous defined types • Base class or parent class or super class -> Derived class or child class( or sub class • Sub class inherits properties from super class
- 8. OOPS Concept – Inheritance Example
- 9. OOPS Concept – Inheritance (Reusability) • If multiple class have common attributes/method, these methods can be moved to common class – parent class • Example: Rectangle and circle method have a common methods move(), which changing the centre co-ordinates
- 10. OOPS Concept – Inheritance (Specialization) • Specialized behavior can be added to the child class • In this case behavior will be implemented in the child class • For example, The implementation of area() method in the circle class is different from the rectangle class
- 11. OOPS Concept – Multiple Inheritance • Inherit properties from more than one class • This is called multiple inheritance • Multiple inheritance is not supported in java (Diamond problem) but is supported in c++
- 12. OOPS Concept – Polymorphism • Polymorphic which means “many forms” has Greek roots • Poly – many • Morphos – forms • Polymorphism gives us the ultimate flexibility in extensibility. The ability to define more than one function with the same name is called Polymorphism. • Method overloading • Method Overriding
- 13. Benefits of Java Language • Simple and powerful • Safe • Object oriented • Robust • Architecture neutral and portable • Compiled and interpreted • Multi threaded • Distributed
- 14. Java is a simple language • Java is designed to be easy for the professional programmer to learn and use.
- 15. Java is a portable • Write once run every where
- 16. Java is a compiled and interpreter language
- 17. Java is robust language • Robust means Strong. Java programs are strong and they don’t crash easily like c and c++. why? • Excellent Exception handling • Memory Management • Class loader sub system of JVM will allocate necessary memory for java program. • Garbage Collector de allocates the memory
- 18. Java for distributed environment • Java is designed for the distributed environment of the Internet. Because it handles TCP/IP protocols • Java supports RMI (Remote Method Invocation). • This feature enables a programmer to invoke methods across the network.
- 19. Getting started - setting up your environment • Download and install jdk6 or jdk7 from oracle.com • Check environment variable for java and javac commands • Check java and javac command from shell or command prompt
- 20. Getting started – Java Tools Tool Name Brief Description appletviewer Run and debug applets without a web browser. apt Annotation processing tool. See Annotation Processing Tool for program annotation processing. extcheck Utility to detect Jar conflicts. jar Create and manage Java Archive (JAR) files. See Java Archive Files page for the JAR specification. java The launcher for Java applications. In this release, a single launcher is used both for development and deployment. The old deployment launcher, jre, is no longer provided. javac The compiler for the Java programming language. javadoc API documentation generator. See Javadoc Tool page for doclet and taglet APIs. javah C header and stub generator. Used to write native methods. javap Class file disassembler jdb The Java Debugger. See JPDA for the debugger architecture specifications.
- 21. Getting started - Writing first java program • Writing First Hello world java program • Compiling and running java program