Updated java

java.html.markdown

@@ -24,26 +24,26 @@ import java.util.ArrayList;
 // Import all classes inside of java.lang package
 import java.security.*;
 
-// Inside of the LearnJava class, is your program's
-// starting point. The main method.
-public class LearnJava
-{
-    //main method
-    public static void main (String[] args)
-    {
+// Each .java file contains one public class, with the same name as the file.
+public class LearnJava {
 
-System.out.println("->Printing");
-// Printing, and forcing a new line on next print, use println()
+    // A program must have a main method as an entry point
+    public static void main (String[] args) {
+
+        // Use System.out.println to print lines
         System.out.println("Hello World!");
         System.out.println("Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true);
-// Printing, without forcing a new line on next print, use print()
-System.out.print("Hello World - ");
-System.out.print("Integer: "+10+" Double: "+3.14+ " Boolean: "+true);
+
+        // To print without a newline, use System.out.print
+        System.out.print("Hello ");
+        System.out.print("World");
+
 
         ///////////////////////////////////////
-// Types
+        // Types & Variables
         ///////////////////////////////////////
-System.out.println("\n\n->Types");
+
+        // Declare a variable using <type> <name> [
         // Byte - 8-bit signed two's complement integer
         // (-128 <= byte <= 127)
         byte fooByte = 100;
@@ -68,18 +68,19 @@ float fooFloat = 234.5f;
         // Double - Double-precision 64-bit IEEE 754 Floating Point
         double fooDouble = 123.4;
 
-// Boolean - True & False
+        // Boolean - true & false
         boolean fooBoolean = true;
         boolean barBoolean = false;
 
         // Char - A single 16-bit Unicode character
         char fooChar = 'A';
 
-// Make a variable a constant
+        // Use final to make a variable immutable
         final int HOURS_I_WORK_PER_WEEK = 9001;
 
         // Strings
         String fooString = "My String Is Here!";
+
         // \n is an escaped character that starts a new line
         String barString = "Printing on a new line?\nNo Problem!";
         System.out.println(fooString);
@@ -99,11 +100,9 @@ int [] y = {9000, 1000, 1337};
         // Indexing an array - Accessing an element
         System.out.println("intArray @ 0: " + intArray[0]);
 
-// Arrays are mutable; it's just memory!
+        // Arrays are zero-indexed and mutable.
         intArray[1] = 1;
         System.out.println("intArray @ 1: " + intArray[1]); // => 1
-intArray[1] = 2;
-System.out.println("intArray @ 1: "+intArray[1]); // => 2
 
         // Others to check out
         // ArrayLists - Like arrays except more functionality is offered,
@@ -159,6 +158,8 @@ System.out.println(--i); //i = 0. Pre-Decrementation
         // Control Structures
         ///////////////////////////////////////
         System.out.println("\n->Control Structures");
+
+        // If statements are c-like
         if (false){
             System.out.println("I never run");
         }else if (false) {
@@ -192,14 +193,14 @@ System.out.println("fooDoWhile Value: "+fooDoWhile);
         // For Loop
         int fooFor;
         //for loop structure => for(<start_statement>; <conditional>; <step>)
-for(fooFor=0;fooFor<100;fooFor++){
+        for(fooFor=0; fooFor<10; fooFor++){
             //System.out.println(fooFor);
-	//Iterated 99 times, fooFor 0->99
+            //Iterated 10 times, fooFor 0->9
         }
         System.out.println("fooFor Value: " + fooFor);
 
         // Switch Case
-int month = 8;
+        int month = 3;
         String monthString;
         switch (month){
             case 1:  monthString = "January";
@@ -208,29 +209,12 @@ switch (month){
                     break;
             case 3:  monthString = "March";
                     break;
-    case 4:  monthString = "April";
-             break;
-    case 5:  monthString = "May";
-             break;
-    case 6:  monthString = "June";
-             break;
-    case 7:  monthString = "July";
-             break;
-    case 8:  monthString = "August";
-             break;
-    case 9:  monthString = "September";
-             break;
-    case 10: monthString = "October";
-             break;
-    case 11: monthString = "November";
-             break;
-    case 12: monthString = "December";
-             break;
-    default: monthString = "Invalid month";
+            default: monthString = "Some other month";
                     break;
         }
         System.out.println("Switch Case Result: " + monthString);
 
+
         ///////////////////////////////////////
         // Converting Data Types And Typcasting
         ///////////////////////////////////////
@@ -251,42 +235,46 @@ Integer.toString(123);//returns a string version of 123
         // Typecasting
         // You can also cast java objects, there's a lot of details and
         // deals with some more intermediate concepts.
-// Feel free to check it out here: http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
+        // Feel free to check it out here:
+        // http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
 
 
         ///////////////////////////////////////
         // Classes And Functions
         ///////////////////////////////////////
 
-	// Read about the class, and function syntax before
-	// reading this.
         System.out.println("\n->Classes & Functions");
-	// Call bicycle's constructor
+
+        // (definition of the Bicycle class follows)
+
+        // Use new to instantiate a class
         Bicycle trek = new Bicycle();
-	// Manipulate your object
+
+        // Call object methods
         trek.speedUp(3);
         trek.setCadence(100);
+
+        // toString is a convention
         System.out.println("trek info: " + trek.toString());
 
-	// Classes Syntax:
+    } // End main method
+} // End LearnJava class
+
+
+// You can include other, non-public classes in a .java file
+
+
+// Class Declaration Syntax:
 // <public/private/protected> class <class name>{
 //    //data fields, constructors, functions all inside
 // }
-	// Function Syntax:
-	// <public/private/protected> <return type> <function name>(<args>)
-	// Here is a quick rundown on access level modifiers (public, private, etc.)
-	// http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html
 
-// This bracket ends the main method
-}
-    // The static field is only required because this class
-    // is nested inside of the learnjava.java class.
-    public static class Bicycle {
+class Bicycle {
 
     // Bicycle's Fields/Variables
-        public int cadence;
-        public int gear;
-        public int speed;
+    public int cadence; // Public: Can be accessed from anywhere
+    private int speed;  // Private: Only accessable from within the class
+    protected int gear; // Protected: Accessible from the class and subclasses
 
     // Constructors are a way of creating classes
     // This is a default constructor
@@ -303,8 +291,18 @@ Integer.toString(123);//returns a string version of 123
         speed = startSpeed;
     }
 
-        // the Bicycle class has
-        // four functions/methods
+    // Function Syntax:
+    // <public/private/protected> <return type> <function name>(<args>)
+
+    // Java classes often implement getters and setters for their fields
+
+    // Method declaration syntax:
+    // <scope> <return type> <method name>(<args>)
+    public int getCadence() {
+        return cadence;
+    }
+
+    // void methods require no return statement
     public void setCadence(int newValue) {
         cadence = newValue;
     }
@@ -313,22 +311,37 @@ Integer.toString(123);//returns a string version of 123
         gear = newValue;
     }
 
-        public void applyBrake(int decrement) {
-            speed -= decrement;
-        }
-
     public void speedUp(int increment) {
         speed += increment;
     }
 
+    public void slowDown(int decrement) {
+        speed -= decrement;
+    }
+
     public String toString() {
         return "gear: "+Integer.toString(gear)+
                 " cadence: "+Integer.toString(cadence)+
                 " speed: "+Integer.toString(speed);
     }
-    // bracket to close nested Bicycle class
+} // end class Bicycle
+
+// Use `extends` to extend a class
+class PennyFarthing extends Bicycle {
+    // (Penny Farthings are those bicycles with the big front wheel.
+    // They have no gears.)
+
+    public PennyFarthing(int startCadence, int startSpeed){
+        // Call the parent constructor with super
+        super(startCadence, startSpeed, 0);
     }
-// bracket to close learnjava.java
+
+    // You should mark a method you're overriding with an @annotation
+    @Override
+    public void setGear(int gear) {
+        gear = 0;
+    }
+
 }
 
 ```