Tuesday 25 September 2018

Java Basics for Android

  • Originated in late 1995, released to public in 1996 (called Oak)
  • Nine major release since the beginning
  • Current version is SDK 8.
  • More than a programming language, it is a execution platform
            - Java Virtual Machine (JVM)

Evaluation of Java Language



Java Features

As released in the "White Paper" by the authors of Java
  1. Simple
  2. Object-Oriented
  3. Distributed
  4. Robust
  5. Secure
  6. Architecture-Neutral
  7. Portable
  8. Interpreted
  9. High-Performance
  10. Multithreaded
  11. Dynamic

JVM (Java Virtual Machine)
  • "Compile once run any where"
  • Java bytecodes
           Java Program                             Java bytecodes
                                    Java Compiler
                                                             →
         Java bytecodes                               Execution
                                      JRE
                                                           →


Execution Path
  • Windows
            - Environment variables
  • Linux
           edit ~ ./bashrc or ~./ cshrs ...
                - set path
                - export PATH
  • To test your settings
            - java - version

Java Naming Conventions

           Java is case-sensitive:
              HelloWorld             ≠           Helloworld



Java Interfaces

Set of requirements
      Describes what a class should do
             E.g. Comparable interface
                 public interface Comparable{
                        int compare To (Object other)
                 }
  • All methods are automatically public
  • All fields are public and static
  • No instance fields
  • No implementation of methods
         - Classes implement the interface
  • Can not instantiate an interface
         - Can declare interface variable
         - Instance of to check

Interfaces & Abstract Classes
  • A class can extend only a single class
  • A class can implement as many interfaces as it likes
          - Provides similar functionality as C++ multiple inheritance.

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