Updated java

java.html.markdown

@@ -24,273 +24,261 @@ import java.util.ArrayList;
 // Import all classes inside of java.lang package
 import java.security.*;
 
-// Inside of the LearnJava class, is your program's
+// Each .java file contains one public class, with the same name as the file.
-// starting point. The main method.
+public class LearnJava {
-public class LearnJava
-{
-    //main method
-    public static void main (String[] args)
-    {
 
-System.out.println("->Printing");
+    // A program must have a main method as an entry point
-// Printing, and forcing a new line on next print, use println()
+    public static void main (String[] args) {
-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);
 
-///////////////////////////////////////
+        // Use System.out.println to print lines
-// Types
+        System.out.println("Hello World!");
-///////////////////////////////////////
+        System.out.println("Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true);
-System.out.println("\n\n->Types");
-// Byte - 8-bit signed two's complement integer
-// (-128 <= byte <= 127)
-byte fooByte = 100;
 
-// Short - 16-bit signed two's complement integer
+        // To print without a newline, use System.out.print
-// (-32,768 <= short <= 32,767)
+        System.out.print("Hello ");
-short fooShort = 10000;
+        System.out.print("World");
 
-// Integer - 32-bit signed two's complement integer
-// (-2,147,483,648 <= int <= 2,147,483,647)
-int fooInt = 1;
 
-// Long - 64-bit signed two's complement integer
+        ///////////////////////////////////////
-// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
+        // Types & Variables
-long fooLong = 100000L;
+        ///////////////////////////////////////
 
-// (Java has no unsigned types)
+        // Declare a variable using <type> <name> [
+        // Byte - 8-bit signed two's complement integer
+        // (-128 <= byte <= 127)
+        byte fooByte = 100;
 
-// Float - Single-precision 32-bit IEEE 754 Floating Point
+        // Short - 16-bit signed two's complement integer
-float fooFloat = 234.5f;
+        // (-32,768 <= short <= 32,767)
+        short fooShort = 10000;
 
-// Double - Double-precision 64-bit IEEE 754 Floating Point
+        // Integer - 32-bit signed two's complement integer
-double fooDouble = 123.4;
+        // (-2,147,483,648 <= int <= 2,147,483,647)
+        int fooInt = 1;
 
-// Boolean - True & False
+        // Long - 64-bit signed two's complement integer
-boolean fooBoolean = true;
+        // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
-boolean barBoolean = false;
+        long fooLong = 100000L;
 
-// Char - A single 16-bit Unicode character
+        // (Java has no unsigned types)
-char fooChar = 'A';
 
-// Make a variable a constant
+        // Float - Single-precision 32-bit IEEE 754 Floating Point
-final int HOURS_I_WORK_PER_WEEK = 9001;
+        float fooFloat = 234.5f;
 
-// Strings
+        // Double - Double-precision 64-bit IEEE 754 Floating Point
-String fooString = "My String Is Here!";
+        double fooDouble = 123.4;
-// \n is an escaped character that starts a new line
-String barString = "Printing on a new line?\nNo Problem!";
-System.out.println(fooString);
-System.out.println(barString);
 
-// Arrays
+        // Boolean - true & false
-//The array size must be decided upon declaration
+        boolean fooBoolean = true;
-//The format for declaring an array is follows:
+        boolean barBoolean = false;
-//<datatype> [] <var name> = new <datatype>[<array size>];
-int [] intArray = new int[10];
-String [] stringArray = new String[1];
-boolean [] booleanArray = new boolean[100];
 
-// Another way to declare & initialize an array
+        // Char - A single 16-bit Unicode character
-int [] y = {9000, 1000, 1337};
+        char fooChar = 'A';
 
-// Indexing an array - Accessing an element
+        // Use final to make a variable immutable
-System.out.println("intArray @ 0: "+intArray[0]);
+        final int HOURS_I_WORK_PER_WEEK = 9001;
 
-// Arrays are mutable; it's just memory!
+        // Strings
-intArray[1] = 1;
+        String fooString = "My String Is Here!";
-System.out.println("intArray @ 1: "+intArray[1]); // => 1
-intArray[1] = 2;
-System.out.println("intArray @ 1: "+intArray[1]); // => 2
 
-// Others to check out
+        // \n is an escaped character that starts a new line
-// ArrayLists - Like arrays except more functionality is offered,
+        String barString = "Printing on a new line?\nNo Problem!";
-//             and the size is mutable
+        System.out.println(fooString);
-// LinkedLists
+        System.out.println(barString);
-// Maps
-// HashMaps
 
-///////////////////////////////////////
+        // Arrays
-// Operators
+        //The array size must be decided upon declaration
-///////////////////////////////////////
+        //The format for declaring an array is follows:
-System.out.println("\n->Operators");
+        //<datatype> [] <var name> = new <datatype>[<array size>];
+        int [] intArray = new int[10];
+        String [] stringArray = new String[1];
+        boolean [] booleanArray = new boolean[100];
 
-int i1 = 1, i2 = 2; // Shorthand for multiple declarations
+        // Another way to declare & initialize an array
+        int [] y = {9000, 1000, 1337};
 
-// Arithmetic is straightforward
+        // Indexing an array - Accessing an element
-System.out.println("1+2 = "+(i1 + i2)); // => 3
+        System.out.println("intArray @ 0: " + intArray[0]);
-System.out.println("2-1 = "+(i2 - i1)); // => 1
-System.out.println("2*1 = "+(i2 * i1)); // => 2
-System.out.println("1/2 = "+(i1 / i2)); // => 0 (0.5, but truncated towards 0)
 
-// Modulo
+        // Arrays are zero-indexed and mutable.
-System.out.println("11%3 = "+(11 % 3)); // => 2
+        intArray[1] = 1;
+        System.out.println("intArray @ 1: " + intArray[1]); // => 1
 
-// Comparison operators
+        // Others to check out
-System.out.println("3 == 2? "+(3 == 2)); // => 0 (false)
+        // ArrayLists - Like arrays except more functionality is offered,
-System.out.println("3 != 2? "+(3 != 2)); // => 1 (true)
+        //             and the size is mutable
-System.out.println("3 > 2? "+(3 > 2)); // => 1
+        // LinkedLists
-System.out.println("3 < 2? "+(3 < 2)); // => 0
+        // Maps
-System.out.println("2 <= 2? "+(2 <= 2)); // => 1
+        // HashMaps
-System.out.println("2 >= 2? "+(2 >= 2)); // => 1
 
-// Bitwise operators!
+        ///////////////////////////////////////
-/*
+        // Operators
-~       Unary bitwise complement
+        ///////////////////////////////////////
-<<      Signed left shift
+        System.out.println("\n->Operators");
->>      Signed right shift
->>>     Unsigned right shift
-&       Bitwise AND
-^       Bitwise exclusive OR
-|       Bitwise inclusive OR
-*/
 
-// Incrementations
+        int i1 = 1, i2 = 2; // Shorthand for multiple declarations
-int i=0;
-System.out.println("\n->Inc/Dec-rementation");
-System.out.println(i++); //i = 1. Post-Incrementation
-System.out.println(++i); //i = 2. Pre-Incrementation
-System.out.println(i--); //i = 1. Post-Decrementation
-System.out.println(--i); //i = 0. Pre-Decrementation
 
-///////////////////////////////////////
+        // Arithmetic is straightforward
-// Control Structures
+        System.out.println("1+2 = " + (i1 + i2)); // => 3
-///////////////////////////////////////
+        System.out.println("2-1 = " + (i2 - i1)); // => 1
-System.out.println("\n->Control Structures");
+        System.out.println("2*1 = " + (i2 * i1)); // => 2
-if (false){
+        System.out.println("1/2 = " + (i1 / i2)); // => 0 (0.5, but truncated towards 0)
+
+        // Modulo
+        System.out.println("11%3 = "+(11 % 3)); // => 2
+
+        // Comparison operators
+        System.out.println("3 == 2? " + (3 == 2)); // => 0 (false)
+        System.out.println("3 != 2? " + (3 != 2)); // => 1 (true)
+        System.out.println("3 > 2? " + (3 > 2)); // => 1
+        System.out.println("3 < 2? " + (3 < 2)); // => 0
+        System.out.println("2 <= 2? " + (2 <= 2)); // => 1
+        System.out.println("2 >= 2? " + (2 >= 2)); // => 1
+
+        // Bitwise operators!
+        /*
+        ~       Unary bitwise complement
+        <<      Signed left shift
+        >>      Signed right shift
+        >>>     Unsigned right shift
+        &       Bitwise AND
+        ^       Bitwise exclusive OR
+        |       Bitwise inclusive OR
+        */
+
+        // Incrementations
+        int i=0;
+        System.out.println("\n->Inc/Dec-rementation");
+        System.out.println(i++); //i = 1. Post-Incrementation
+        System.out.println(++i); //i = 2. Pre-Incrementation
+        System.out.println(i--); //i = 1. Post-Decrementation
+        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) {
+        }else if (false) {
             System.out.println("I am also never run");
-} else {
+        } else {
             System.out.println("I print");
-}
+        }
 
-// While loop
+        // While loop
-int fooWhile = 0;
+        int fooWhile = 0;
-while(fooWhile < 100)
+        while(fooWhile < 100)
-{
+        {
             //System.out.println(fooWhile);
             //Increment the counter
             //Iterated 99 times, fooWhile 0->99
             fooWhile++;
-}
+        }
-System.out.println("fooWhile Value: "+fooWhile);
+        System.out.println("fooWhile Value: " + fooWhile);
 
-// Do While Loop
+        // Do While Loop
-int fooDoWhile = 0;
+        int fooDoWhile = 0;
-do
+        do
-{
+        {
             //System.out.println(fooDoWhile);
             //Increment the counter
             //Iterated 99 times, fooDoWhile 0->99
             fooDoWhile++;
-}while(fooDoWhile < 100);
+        }while(fooDoWhile < 100);
-System.out.println("fooDoWhile Value: "+fooDoWhile);
+        System.out.println("fooDoWhile Value: " + fooDoWhile);
 
-// For Loop
+        // For Loop
-int fooFor;
+        int fooFor;
-//for loop structure => for(<start_statement>;<conditional>;<step>)
+        //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);
+        System.out.println("fooFor Value: " + fooFor);
 
-// Switch Case
+        // Switch Case
-int month = 8;
+        int month = 3;
-String monthString;
+        String monthString;
-switch (month){
+        switch (month){
             case 1:  monthString = "January";
                     break;
             case 2:  monthString = "February";
                     break;
             case 3:  monthString = "March";
                     break;
-    case 4:  monthString = "April";
+            default: monthString = "Some other month";
                     break;
-    case 5:  monthString = "May";
+        }
-             break;
+        System.out.println("Switch Case Result: " + monthString);
-    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";
-             break;
-}
-System.out.println("Switch Case Result: "+monthString);
-
-///////////////////////////////////////
-// Converting Data Types And Typcasting
-///////////////////////////////////////
-
-// Converting data
-
-// Convert String To Integer
-Integer.parseInt("123");//returns an integer version of "123"
-
-// Convert Integer To String
-Integer.toString(123);//returns a string version of 123
-
-// For other conversions check out the following classes:
-// Double
-// Long
-// String
-
-// 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
 
 
-///////////////////////////////////////
+        ///////////////////////////////////////
-// Classes And Functions
+        // Converting Data Types And Typcasting
-///////////////////////////////////////
+        ///////////////////////////////////////
+
+        // Converting data
+
+        // Convert String To Integer
+        Integer.parseInt("123");//returns an integer version of "123"
+
+        // Convert Integer To String
+        Integer.toString(123);//returns a string version of 123
+
+        // For other conversions check out the following classes:
+        // Double
+        // Long
+        // String
+
+        // 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
+
+
+        ///////////////////////////////////////
+        // 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);
-	System.out.println("trek info: "+trek.toString());
 
-	// Classes Syntax:
+        // toString is a convention
-	// <public/private/protected> class <class name>{
+        System.out.println("trek info: " + trek.toString());
-	//    //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
+    } // End main method
-}
+} // End LearnJava class
-    // The static field is only required because this class
+
-    // is nested inside of the learnjava.java class.
+
-    public static class Bicycle {
+// 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
+// }
+
+class Bicycle {
 
     // Bicycle's Fields/Variables
-        public int cadence;
+    public int cadence; // Public: Can be accessed from anywhere
-        public int gear;
+    private int speed;  // Private: Only accessable from within the class
-        public int speed;
+    protected int gear; // Protected: Accessible from the class and subclasses
 
     // Constructors are a way of creating classes
     // This is a default constructor
-        public Bicycle(){
+    public Bicycle() {
         gear = 1;
         cadence = 50;
         speed = 5;
@@ -303,8 +291,18 @@ Integer.toString(123);//returns a string version of 123
         speed = startSpeed;
     }
 
-        // the Bicycle class has
+    // Function Syntax:
-        // four functions/methods
+    // <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 String toString(){
+    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;
+    }
+
 }
 
 ```