diff options
Diffstat (limited to 'java.html.markdown')
-rw-r--r-- | java.html.markdown | 601 |
1 files changed, 307 insertions, 294 deletions
diff --git a/java.html.markdown b/java.html.markdown index 712233ba..729ff531 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -24,311 +24,324 @@ 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) - { - -System.out.println("->Printing"); -// Printing, and forcing a new line on next print, use println() -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); - -/////////////////////////////////////// -// Types -/////////////////////////////////////// -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 -// (-32,768 <= short <= 32,767) -short fooShort = 10000; - -// 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) -long fooLong = 100000L; - -// (Java has no unsigned types) - -// Float - Single-precision 32-bit IEEE 754 Floating Point -float fooFloat = 234.5f; - -// Double - Double-precision 64-bit IEEE 754 Floating Point -double fooDouble = 123.4; - -// Boolean - True & False -boolean fooBoolean = true; -boolean barBoolean = false; - -// Char - A single 16-bit Unicode character -char fooChar = 'A'; - -// Make a variable a constant -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); -System.out.println(barString); - -// Arrays -//The array size must be decided upon declaration -//The format for declaring an array is follows: -//<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 -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! -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, -// and the size is mutable -// LinkedLists -// Maps -// HashMaps - -/////////////////////////////////////// -// Operators -/////////////////////////////////////// -System.out.println("\n->Operators"); - -int i1 = 1, i2 = 2; // Shorthand for multiple declarations - -// Arithmetic is straightforward -System.out.println("1+2 = "+(i1 + i2)); // => 3 -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 -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 -*/ +// Each .java file contains one public class, with the same name as the file. +public class LearnJava { -// 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 (false){ - System.out.println("I never run"); -}else if (false) { - System.out.println("I am also never run"); -} else { - System.out.println("I print"); -} + // A program must have a main method as an entry point + public static void main (String[] args) { -// While loop -int fooWhile = 0; -while(fooWhile < 100) -{ - //System.out.println(fooWhile); - //Increment the counter - //Iterated 99 times, fooWhile 0->99 - fooWhile++; -} -System.out.println("fooWhile Value: "+fooWhile); - -// Do While Loop -int fooDoWhile = 0; -do -{ - //System.out.println(fooDoWhile); - //Increment the counter - //Iterated 99 times, fooDoWhile 0->99 - fooDoWhile++; -}while(fooDoWhile < 100); -System.out.println("fooDoWhile Value: "+fooDoWhile); - -// For Loop -int fooFor; -//for loop structure => for(<start_statement>;<conditional>;<step>) -for(fooFor=0;fooFor<100;fooFor++){ - //System.out.println(fooFor); - //Iterated 99 times, fooFor 0->99 -} -System.out.println("fooFor Value: "+fooFor); - -// Switch Case -int month = 8; -String monthString; -switch (month){ - case 1: monthString = "January"; - break; - case 2: monthString = "February"; - 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"; - 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 -/////////////////////////////////////// - - // Read about the class, and function syntax before - // reading this. - System.out.println("\n->Classes & Functions"); - // Call bicycle's constructor - Bicycle trek = new Bicycle(); - // Manipulate your object - trek.speedUp(3); - trek.setCadence(100); - System.out.println("trek info: "+trek.toString()); - - // Classes 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 { - - // Bicycle's Fields/Variables - public int cadence; - public int gear; - public int speed; - - // Constructors are a way of creating classes - // This is a default constructor - public Bicycle(){ - gear = 1; - cadence = 50; - speed = 5; - } + // Use System.out.println to print lines + System.out.println("Hello World!"); + System.out.println("Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true); - // This is a specified constructor (it contains arguments) - public Bicycle(int startCadence, int startSpeed, int startGear) { - gear = startGear; - cadence = startCadence; - speed = startSpeed; - } + // To print without a newline, use System.out.print + System.out.print("Hello "); + System.out.print("World"); - // the Bicycle class has - // four functions/methods - public void setCadence(int newValue) { - cadence = newValue; - } - public void setGear(int newValue) { - gear = newValue; + /////////////////////////////////////// + // Types & Variables + /////////////////////////////////////// + + // Declare a variable using <type> <name> [ + // Byte - 8-bit signed two's complement integer + // (-128 <= byte <= 127) + byte fooByte = 100; + + // Short - 16-bit signed two's complement integer + // (-32,768 <= short <= 32,767) + short fooShort = 10000; + + // 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) + long fooLong = 100000L; + + // (Java has no unsigned types) + + // Float - Single-precision 32-bit IEEE 754 Floating Point + float fooFloat = 234.5f; + + // Double - Double-precision 64-bit IEEE 754 Floating Point + double fooDouble = 123.4; + + // Boolean - true & false + boolean fooBoolean = true; + boolean barBoolean = false; + + // Char - A single 16-bit Unicode character + char fooChar = 'A'; + + // 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); + System.out.println(barString); + + // Arrays + //The array size must be decided upon declaration + //The format for declaring an array is follows: + //<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 + int [] y = {9000, 1000, 1337}; + + // Indexing an array - Accessing an element + System.out.println("intArray @ 0: " + intArray[0]); + + // Arrays are zero-indexed and mutable. + intArray[1] = 1; + System.out.println("intArray @ 1: " + intArray[1]); // => 1 + + // Others to check out + // ArrayLists - Like arrays except more functionality is offered, + // and the size is mutable + // LinkedLists + // Maps + // HashMaps + + /////////////////////////////////////// + // Operators + /////////////////////////////////////// + System.out.println("\n->Operators"); + + int i1 = 1, i2 = 2; // Shorthand for multiple declarations + + // Arithmetic is straightforward + System.out.println("1+2 = " + (i1 + i2)); // => 3 + 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 + 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) { + System.out.println("I am also never run"); + } else { + System.out.println("I print"); } - public void applyBrake(int decrement) { - speed -= decrement; + // While loop + int fooWhile = 0; + while(fooWhile < 100) + { + //System.out.println(fooWhile); + //Increment the counter + //Iterated 99 times, fooWhile 0->99 + fooWhile++; } - - public void speedUp(int increment) { - speed += increment; + System.out.println("fooWhile Value: " + fooWhile); + + // Do While Loop + int fooDoWhile = 0; + do + { + //System.out.println(fooDoWhile); + //Increment the counter + //Iterated 99 times, fooDoWhile 0->99 + fooDoWhile++; + }while(fooDoWhile < 100); + System.out.println("fooDoWhile Value: " + fooDoWhile); + + // For Loop + int fooFor; + //for loop structure => for(<start_statement>; <conditional>; <step>) + for(fooFor=0; fooFor<10; fooFor++){ + //System.out.println(fooFor); + //Iterated 10 times, fooFor 0->9 } - - public String toString(){ - return "gear: "+Integer.toString(gear)+ - " cadence: "+Integer.toString(cadence)+ - " speed: "+Integer.toString(speed); + System.out.println("fooFor Value: " + fooFor); + + // Switch Case + int month = 3; + String monthString; + switch (month){ + case 1: monthString = "January"; + break; + case 2: monthString = "February"; + break; + case 3: monthString = "March"; + break; + default: monthString = "Some other month"; + break; } - // bracket to close nested Bicycle class + 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 + /////////////////////////////////////// + + System.out.println("\n->Classes & Functions"); + + // (definition of the Bicycle class follows) + + // Use new to instantiate a class + Bicycle trek = new Bicycle(); + + // Call object methods + trek.speedUp(3); + trek.setCadence(100); + + // toString is a convention + System.out.println("trek info: " + trek.toString()); + + } // 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 +// } + +class Bicycle { + + // Bicycle's Fields/Variables + 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 + public Bicycle() { + gear = 1; + cadence = 50; + speed = 5; + } + + // This is a specified constructor (it contains arguments) + public Bicycle(int startCadence, int startSpeed, int startGear) { + gear = startGear; + cadence = startCadence; + speed = startSpeed; } -// bracket to close learnjava.java + + // 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; + } + + public void setGear(int newValue) { + gear = newValue; + } + + 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); + } +} // 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); + } + + // You should mark a method you're overriding with an @annotation + @Override + public void setGear(int gear) { + gear = 0; + } + } ``` |