Java Basics: Comments, Classes, Constructors, Inheritance

Comments are almost like C++ ,[object Object],/* This kind of comment can span multiple lines */ // This kind is to the end of the line /** * This kind of comment is a special * ‘javadoc’ style comment */

An example of a class class Person { String name; int age; void birthday ( ) { age++; System.out.println (name + ' is now ' + age); } } Variable Method

Scoping ,[object Object],[object Object],{ int x = 12; /* only x available */ { int q = 96; /* both x and q available */ } /* only x available */ /* q “out of scope” */ } { int x = 12; { int x = 96; /* illegal */ } } This is ok in C/C++ but not in Java.

An array is an object ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Scope of Objects ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Methods, arguments and return values ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The static keyword ,[object Object],[object Object],[object Object],[object Object],[object Object],class StaticTest {static int i = 47;} StaticTest st1 = new StaticTest(); StaticTest st2 = new StaticTest(); // st1.i == st2.I == 47 StaticTest.i++; // or st1.I++ or st2.I++ // st1.i == st2.I == 48

Array Operations ,[object Object],[object Object],[object Object],[object Object]

Echo.java C:MBC31ava>type echo.java // This is the Echo example from the Sun tutorial class echo { public static void main(String args[]) { for (int i=0; i < args.length; i++) { System.out.println( args[i] ); } } } C:MBC31ava>javac echo.java C:MBC31ava>java echo this is pretty silly this is pretty silly C:MBC31ava>

Factorial Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],From Java in a Nutshell

JAVA Classes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Constructors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Constructor example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],this.r refers to the r field of the class This() refers to a constructor for the class

Extending a class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Extending a class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Overloading, overwriting, and shadowing ,[object Object],[object Object]

On designing class hierarchies ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Data hiding and encapsulation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example encapsulation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Access control ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Getters and setters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example getters and setters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Abstract classes and methods ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example abstract class ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Syntax Notes ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Java Basics: Comments, Classes, Constructors, Inheritance

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Java Basics: Comments, Classes, Constructors, Inheritance