diff options
Diffstat (limited to 'java.html.markdown')
| -rw-r--r-- | java.html.markdown | 221 |
1 files changed, 112 insertions, 109 deletions
diff --git a/java.html.markdown b/java.html.markdown index 3484aee5..928eb39f 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -1,15 +1,16 @@ --- - language: java contributors: - ["Jake Prather", "http://github.com/JakeHP"] + - ["Jakukyo Friel", "http://weakish.github.io"] - ["Madison Dickson", "http://github.com/mix3d"] + - ["Simon Morgan", "http://sjm.io/"] filename: LearnJava.java - --- -Java is a general-purpose, concurrent, class-based, object-oriented computer programming language. -[Read more here.](http://docs.oracle.com/javase/tutorial/java/index.html) +Java is a general-purpose, concurrent, class-based, object-oriented computer +programming language. +[Read more here.](http://docs.oracle.com/javase/tutorial/java/) ```java // Single-line comments start with // @@ -30,17 +31,17 @@ import java.security.*; // the file. public class LearnJava { - // A program must have a main method as an entry point + // A program must have a main method as an entry point. public static void main (String[] args) { - // Use System.out.println to print lines + // Use System.out.println() to print lines. System.out.println("Hello World!"); System.out.println( "Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true); - // To print without a newline, use System.out.print + // To print without a newline, use System.out.print(). System.out.print("Hello "); System.out.print("World"); @@ -49,7 +50,7 @@ public class LearnJava { // Types & Variables /////////////////////////////////////// - // Declare a variable using <type> <name> [ + // Declare a variable using <type> <name> // Byte - 8-bit signed two's complement integer // (-128 <= byte <= 127) byte fooByte = 100; @@ -68,7 +69,7 @@ public class LearnJava { // L is used to denote that this variable value is of type Long; // anything without is treated as integer by default. - // Note: Java has no unsigned types + // Note: Java has no unsigned types. // Float - Single-precision 32-bit IEEE 754 Floating Point float fooFloat = 234.5f; @@ -85,7 +86,7 @@ public class LearnJava { // Char - A single 16-bit Unicode character char fooChar = 'A'; - // final variables can't be reassigned to another object + // final variables can't be reassigned to another object. final int HOURS_I_WORK_PER_WEEK = 9001; // Strings @@ -100,17 +101,17 @@ public class LearnJava { System.out.println(bazString); // Arrays - //The array size must be decided upon instantiation - //The following formats work for declaring an arrow - //<datatype> [] <var name> = new <datatype>[<array size>]; - //<datatype> <var name>[] = new <datatype>[<array size>]; - int [] intArray = new int[10]; - String [] stringArray = new String[1]; - boolean boolArray [] = new boolean[100]; + // The array size must be decided upon instantiation + // The following formats work for declaring an array + // <datatype>[] <var name> = new <datatype>[<array size>]; + // <datatype> <var name>[] = new <datatype>[<array size>]; + int[] intArray = new int[10]; + String[] stringArray = new String[1]; + boolean boolArray[] = new boolean[100]; // Another way to declare & initialize an array - int [] y = {9000, 1000, 1337}; - String names [] = {"Bob", "John", "Fred", "Juan Pedro"}; + int[] y = {9000, 1000, 1337}; + String names[] = {"Bob", "John", "Fred", "Juan Pedro"}; boolean bools[] = new boolean[] {true, false, false}; // Indexing an array - Accessing an element @@ -121,11 +122,17 @@ public class LearnJava { 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 + // ArrayLists - Like arrays except more functionality is offered, and + // the size is mutable. + // LinkedLists - Implementation of doubly-linked list. All of the + // operations perform as could be expected for a + // doubly-linked list. + // Maps - A set of objects that maps keys to values. A map cannot + // contain duplicate keys; each key can map to at most one value. + // HashMaps - This class uses a hashtable to implement the Map + // interface. This allows the execution time of basic + // operations, such as get and insert element, to remain + // constant even for large sets. /////////////////////////////////////// // Operators @@ -153,13 +160,13 @@ public class LearnJava { // Bitwise operators! /* - ~ Unary bitwise complement - << Signed left shift - >> Signed right shift - >>> Unsigned right shift - & Bitwise AND - ^ Bitwise exclusive OR - | Bitwise inclusive OR + ~ Unary bitwise complement + << Signed left shift + >> Signed right shift + >>> Unsigned right shift + & Bitwise AND + ^ Bitwise exclusive OR + | Bitwise inclusive OR */ // Incrementations @@ -168,10 +175,10 @@ public class LearnJava { // The ++ and -- operators increment and decrement by 1 respectively. // If they are placed before the variable, they increment then return; // after the variable they return then increment. - System.out.println(i++); //i = 1, prints 0 (post-increment) - System.out.println(++i); //i = 2, prints 2 (pre-increment) - System.out.println(i--); //i = 1, prints 2 (post-decrement) - System.out.println(--i); //i = 0, prints 0 (pre-decrement) + System.out.println(i++); // i = 1, prints 0 (post-increment) + System.out.println(++i); // i = 2, prints 2 (pre-increment) + System.out.println(i--); // i = 1, prints 2 (post-decrement) + System.out.println(--i); // i = 0, prints 0 (pre-decrement) /////////////////////////////////////// // Control Structures @@ -190,81 +197,77 @@ public class LearnJava { // While loop int fooWhile = 0; - while(fooWhile < 100) - { - //System.out.println(fooWhile); - //Increment the counter - //Iterated 100 times, fooWhile 0,1,2...99 + while(fooWhile < 100) { + System.out.println(fooWhile); + // Increment the counter + // Iterated 100 times, fooWhile 0,1,2...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 + 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); // 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 + // for loop structure => for(<start_statement>; <conditional>; <step>) + for (fooFor = 0; fooFor < 10; fooFor++) { + System.out.println(fooFor); + // Iterated 10 times, fooFor 0->9 } System.out.println("fooFor Value: " + fooFor); // For Each Loop - // An automatic iteration through an array or list of objects. - int[] fooList = {1,2,3,4,5,6,7,8,9}; - //for each loop structure => for(<object> : <array_object>) - //reads as: for each object in the array - //note: the object type must match the array. - - for( int bar : fooList ){ - //System.out.println(bar); + // The for loop is also able to iterate over arrays as well as objects + // that implement the Iterable interface. + int[] fooList = {1, 2, 3, 4, 5, 6, 7, 8, 9}; + // for each loop structure => for (<object> : <iterable>) + // reads as: for each element in the iterable + // note: the object type must match the element type of the iterable. + + for (int bar : fooList) { + System.out.println(bar); //Iterates 9 times and prints 1-9 on new lines } // Switch Case // A switch works with the byte, short, char, and int data types. - // It also works with enumerated types (discussed in Enum Types), - // the String class, and a few special classes that wrap - // primitive types: Character, Byte, Short, and Integer. + // It also works with enumerated types (discussed in Enum Types), the + // String class, and a few special classes that wrap primitive types: + // Character, Byte, Short, and Integer. int month = 3; String monthString; - switch (month){ - case 1: - monthString = "January"; - break; - case 2: - monthString = "February"; + switch (month) { + case 1: monthString = "January"; break; - case 3: - monthString = "March"; + case 2: monthString = "February"; break; - default: - monthString = "Some other month"; + case 3: monthString = "March"; break; + default: monthString = "Some other month"; + break; } System.out.println("Switch Case Result: " + monthString); // Conditional Shorthand // You can use the '?' operator for quick assignments or logic forks. - // Reads as "If (statement) is true, use <first value>, otherwise, use <second value>" + // Reads as "If (statement) is true, use <first value>, otherwise, use + // <second value>" int foo = 5; String bar = (foo < 10) ? "A" : "B"; System.out.println(bar); // Prints A, because the statement is true - /////////////////////////////////////// - // Converting Data Types And Typcasting - /////////////////////////////////////// + //////////////////////////////////////// + // Converting Data Types And Typecasting + //////////////////////////////////////// // Converting data @@ -280,9 +283,8 @@ public class LearnJava { // 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: + // 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 @@ -312,9 +314,9 @@ public class LearnJava { // Class Declaration Syntax: -// <public/private/protected> class <class name>{ -// //data fields, constructors, functions all inside. -// //functions are called as methods in Java. +// <public/private/protected> class <class name> { +// // data fields, constructors, functions all inside. +// // functions are called as methods in Java. // } class Bicycle { @@ -335,7 +337,8 @@ class Bicycle { } // This is a constructor that takes arguments - public Bicycle(int startCadence, int startSpeed, int startGear, String name) { + public Bicycle(int startCadence, int startSpeed, int startGear, + String name) { this.gear = startGear; this.cadence = startCadence; this.speed = startSpeed; @@ -381,10 +384,8 @@ class Bicycle { //Method to display the attribute values of this Object. @Override public String toString() { - return "gear: " + gear + - " cadence: " + cadence + - " speed: " + speed + - " name: " + name; + return "gear: " + gear + " cadence: " + cadence + " speed: " + speed + + " name: " + name; } } // end class Bicycle @@ -398,26 +399,26 @@ class PennyFarthing extends Bicycle { super(startCadence, startSpeed, 0, "PennyFarthing"); } - // You should mark a method you're overriding with an @annotation - // To learn more about what annotations are and their purpose - // check this out: http://docs.oracle.com/javase/tutorial/java/annotations/ + // You should mark a method you're overriding with an @annotation. + // To learn more about what annotations are and their purpose check this + // out: http://docs.oracle.com/javase/tutorial/java/annotations/ @Override public void setGear(int gear) { gear = 0; } - } -//Interfaces -//Interface declaration syntax -//<access-level> interface <interface-name> extends <super-interfaces> { -// //Constants -// //Method declarations -//} +// Interfaces +// Interface declaration syntax +// <access-level> interface <interface-name> extends <super-interfaces> { +// // Constants +// // Method declarations +// } -//Example - Food: +// Example - Food: public interface Edible { - public void eat(); //Any class that implements this interface, must implement this method + public void eat(); // Any class that implements this interface, must + // implement this method. } public interface Digestible { @@ -425,29 +426,31 @@ public interface Digestible { } -//We can now create a class that implements both of these interfaces +// We can now create a class that implements both of these interfaces. public class Fruit implements Edible, Digestible { + @Override public void eat() { - //... + // ... } + @Override public void digest() { - //... + // ... } } -//In java, you can extend only one class, but you can implement many interfaces. -//For example: -public class ExampleClass extends ExampleClassParent implements InterfaceOne, InterfaceTwo { +// In Java, you can extend only one class, but you can implement many +// interfaces. For example: +public class ExampleClass extends ExampleClassParent implements InterfaceOne, + InterfaceTwo { + @Override public void InterfaceOneMethod() { - } + @Override public void InterfaceTwoMethod() { - } } - ``` ## Further Reading @@ -484,8 +487,8 @@ The links provided here below are just to get an understanding of the topic, fee * [Head First Java](http://www.headfirstlabs.com/books/hfjava/) +* [Thinking in Java](http://www.mindview.net/Books/TIJ/) + * [Objects First with Java](http://www.amazon.com/Objects-First-Java-Practical-Introduction/dp/0132492660) * [Java The Complete Reference](http://www.amazon.com/gp/product/0071606300) - - |