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.