From 8e388cd3344b90cfdc02741359850a2352a8f9b7 Mon Sep 17 00:00:00 2001 From: Dhwani Shah Date: Fri, 2 Oct 2015 14:30:45 -0500 Subject: Added section on how to declare and initialize both single varible and multiple varibles with the same value. Important concept for large structured programs. Seperated this a little bit. --- java.html.markdown | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 928eb39f..0f5b39af 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -47,10 +47,30 @@ public class LearnJava { /////////////////////////////////////// - // Types & Variables + // Variables /////////////////////////////////////// - + + /* + * Variable Declaration + */ // Declare a variable using + int fooInt; + // Declare multiple variables of same type , , + int fooInt1, fooInt2, fooInt3; + + /* + * Variable Initialization + */ + + // Initialize a variable using = + int fooInt = 1; + // Initialize multiple variables of same type with same value , , = + int fooInt1, fooInt2, fooInt3; + fooInt1 = fooInt2 = fooInt3 = 1; + + /* + * Variable types + */ // Byte - 8-bit signed two's complement integer // (-128 <= byte <= 127) byte fooByte = 100; -- cgit v1.2.3 From 231cd629cab3553d126f8cca04a034c995c4668f Mon Sep 17 00:00:00 2001 From: Dhwani Shah Date: Fri, 2 Oct 2015 14:45:25 -0500 Subject: Update java.html.markdown --- java.html.markdown | 104 ++++++++--------------------------------------------- 1 file changed, 14 insertions(+), 90 deletions(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 0f5b39af..745741f8 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -1,18 +1,3 @@ ---- -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/) - -```java // Single-line comments start with // /* Multi-line comments look like this. @@ -47,30 +32,10 @@ public class LearnJava { /////////////////////////////////////// - // Variables + // Types & Variables /////////////////////////////////////// - - /* - * Variable Declaration - */ - // Declare a variable using - int fooInt; - // Declare multiple variables of same type , , - int fooInt1, fooInt2, fooInt3; - /* - * Variable Initialization - */ - - // Initialize a variable using = - int fooInt = 1; - // Initialize multiple variables of same type with same value , , = - int fooInt1, fooInt2, fooInt3; - fooInt1 = fooInt2 = fooInt3 = 1; - - /* - * Variable types - */ + // Declare a variable using // Byte - 8-bit signed two's complement integer // (-128 <= byte <= 127) byte fooByte = 100; @@ -437,26 +402,26 @@ class PennyFarthing extends Bicycle { // Example - Food: public interface Edible { - public void eat(); // Any class that implements this interface, must + public void eat(); // Any class that implements this interface, must // implement this method. } public interface Digestible { - public void digest(); + public void digest(); } // We can now create a class that implements both of these interfaces. public class Fruit implements Edible, Digestible { @Override - public void eat() { - // ... - } + public void eat() { + // ... + } @Override - public void digest() { - // ... - } + public void digest() { + // ... + } } // In Java, you can extend only one class, but you can implement many @@ -464,51 +429,10 @@ public class Fruit implements Edible, Digestible { public class ExampleClass extends ExampleClassParent implements InterfaceOne, InterfaceTwo { @Override - public void InterfaceOneMethod() { - } + public void InterfaceOneMethod() { + } @Override - public void InterfaceTwoMethod() { - } + public void InterfaceTwoMethod() { + } } -``` - -## Further Reading - -The links provided here below are just to get an understanding of the topic, feel free to Google and find specific examples. - -**Official Oracle Guides**: - -* [Java Tutorial Trail from Sun / Oracle](http://docs.oracle.com/javase/tutorial/index.html) - -* [Java Access level modifiers](http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html) - -* [Object-Oriented Programming Concepts](http://docs.oracle.com/javase/tutorial/java/concepts/index.html): - * [Inheritance](http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html) - * [Polymorphism](http://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html) - * [Abstraction](http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html) - -* [Exceptions](http://docs.oracle.com/javase/tutorial/essential/exceptions/index.html) - -* [Interfaces](http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html) - -* [Generics](http://docs.oracle.com/javase/tutorial/java/generics/index.html) - -* [Java Code Conventions](http://www.oracle.com/technetwork/java/codeconv-138413.html) - -**Online Practice and Tutorials** - -* [Learneroo.com - Learn Java](http://www.learneroo.com) - -* [Codingbat.com](http://codingbat.com/java) - - -**Books**: - -* [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) -- cgit v1.2.3 From c7240369b6465f2a736cb61d1bff89c971e76929 Mon Sep 17 00:00:00 2001 From: Dhwani Shah Date: Fri, 2 Oct 2015 14:47:17 -0500 Subject: Update java.html.markdown --- java.html.markdown | 80 ++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 68 insertions(+), 12 deletions(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 745741f8..928eb39f 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -1,3 +1,18 @@ +--- +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/) + +```java // Single-line comments start with // /* Multi-line comments look like this. @@ -402,26 +417,26 @@ class PennyFarthing extends Bicycle { // Example - Food: public interface Edible { - public void eat(); // Any class that implements this interface, must + public void eat(); // Any class that implements this interface, must // implement this method. } public interface Digestible { - public void digest(); + public void digest(); } // We can now create a class that implements both of these interfaces. public class Fruit implements Edible, Digestible { @Override - public void eat() { - // ... - } + public void eat() { + // ... + } @Override - public void digest() { - // ... - } + public void digest() { + // ... + } } // In Java, you can extend only one class, but you can implement many @@ -429,10 +444,51 @@ public class Fruit implements Edible, Digestible { public class ExampleClass extends ExampleClassParent implements InterfaceOne, InterfaceTwo { @Override - public void InterfaceOneMethod() { - } + public void InterfaceOneMethod() { + } @Override - public void InterfaceTwoMethod() { - } + public void InterfaceTwoMethod() { + } } +``` + +## Further Reading + +The links provided here below are just to get an understanding of the topic, feel free to Google and find specific examples. + +**Official Oracle Guides**: + +* [Java Tutorial Trail from Sun / Oracle](http://docs.oracle.com/javase/tutorial/index.html) + +* [Java Access level modifiers](http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html) + +* [Object-Oriented Programming Concepts](http://docs.oracle.com/javase/tutorial/java/concepts/index.html): + * [Inheritance](http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html) + * [Polymorphism](http://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html) + * [Abstraction](http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html) + +* [Exceptions](http://docs.oracle.com/javase/tutorial/essential/exceptions/index.html) + +* [Interfaces](http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html) + +* [Generics](http://docs.oracle.com/javase/tutorial/java/generics/index.html) + +* [Java Code Conventions](http://www.oracle.com/technetwork/java/codeconv-138413.html) + +**Online Practice and Tutorials** + +* [Learneroo.com - Learn Java](http://www.learneroo.com) + +* [Codingbat.com](http://codingbat.com/java) + + +**Books**: + +* [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) -- cgit v1.2.3 From 63793af2e955f8a8abe698c4a70809cfbff63452 Mon Sep 17 00:00:00 2001 From: Dhwani Shah Date: Fri, 2 Oct 2015 14:54:09 -0500 Subject: Added section on how to declare and initialize both single varible and multiple varibles with the same value. Important concept for large structured programs. Seperated this a little bit. --- java.html.markdown | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 928eb39f..1aa06570 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -47,10 +47,30 @@ public class LearnJava { /////////////////////////////////////// - // Types & Variables + // Variables /////////////////////////////////////// - + + /* + * Variable Declaration + */ // Declare a variable using + int fooInt; + // Declare multiple variables of the same type , , + int fooInt1, fooInt2, fooInt3; + + /* + * Variable Initialization + */ + + // Initialize a variable using = + int fooInt = 1; + // Initialize multiple variables of same type with same value , , = + int fooInt1, fooInt2, fooInt3; + fooInt1 = fooInt2 = fooInt3 = 1; + + /* + * Variable types + */ // Byte - 8-bit signed two's complement integer // (-128 <= byte <= 127) byte fooByte = 100; -- cgit v1.2.3 From 6b6f88c64d9a4b2d26de5725dee24f3c459fb93c Mon Sep 17 00:00:00 2001 From: bk2dcradle Date: Sun, 4 Oct 2015 01:47:09 +0530 Subject: Added abstract classes --- java.html.markdown | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 928eb39f..2f41be81 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -451,6 +451,74 @@ public class ExampleClass extends ExampleClassParent implements InterfaceOne, public void InterfaceTwoMethod() { } } + + +// Abstract Classes +// Abstract Class declaration syntax +// abstract extends { +// // Constants and variables +// // Method declarations +// } + +// Methods can't have bodies in an interface, unless the method is +// static. Also variables are NOT final by default, unlike an interface. +// Also abstract classes CAN have the "main" method. +// Abstract classes solve these problems. + +public abstract class Animal +{ + public abstract void makeSound(); + + // Method can have a body + public void eat() + { + System.out.println("I am an animal and I am Eating."); + // Note: We can access private variable here. + age = 30; + } + + // No need to initialise, however in an interface + // a variable is implicitly final and hence has + // to be initialised. + private int age; + + public void printAge() + { + System.out.println(age); + } + + // Abstract classes can have main function. + public static void main(String[] args) + { + System.out.println("I am abstract"); + } +} + +class Dog extends Animal +{ + // Note still have to override the abstract methods in the + // abstract class. + @Override + public void makeSound() + { + System.out.println("Bark"); + // age = 30; ==> ERROR! age is private to Animal + } + + // NOTE: You will get an error if you used the + // @Override annotation here, since java doesn't allow + // overriding of static methods. + // What is happening here is called METHOD HIDING. + // Check out this awesome SO post: (http://stackoverflow.com/questions/16313649/) + public static void main(String[] args) + { + Dog pluto = new Dog(); + pluto.makeSound(); + pluto.eat(); + pluto.printAge(); + } +} + ``` ## Further Reading -- cgit v1.2.3 From d8efd3ba3416669177683887b2822eb5d56c157b Mon Sep 17 00:00:00 2001 From: bk2dcradle Date: Mon, 5 Oct 2015 01:38:02 +0530 Subject: Modified as said to by a Collaborator --- java.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index 2f41be81..89a710ee 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -477,9 +477,9 @@ public abstract class Animal age = 30; } - // No need to initialise, however in an interface + // No need to initialize, however in an interface // a variable is implicitly final and hence has - // to be initialised. + // to be initialized. private int age; public void printAge() @@ -509,7 +509,7 @@ class Dog extends Animal // @Override annotation here, since java doesn't allow // overriding of static methods. // What is happening here is called METHOD HIDING. - // Check out this awesome SO post: (http://stackoverflow.com/questions/16313649/) + // Check out this awesome SO post: http://stackoverflow.com/questions/16313649/ public static void main(String[] args) { Dog pluto = new Dog(); -- cgit v1.2.3 From 8b456426407997fdbb8a0befb4181a513e585231 Mon Sep 17 00:00:00 2001 From: Per Lilja Date: Mon, 5 Oct 2015 20:29:05 +0200 Subject: Added description for Double Brace Initialization --- java.html.markdown | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index e4234a39..b4757962 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -325,6 +325,33 @@ public class LearnJava { // toString returns this Object's string representation. System.out.println("trek info: " + trek.toString()); + + // Double Brace Initialization + // The Java Language has no syntax for how to create static Collections + // in an easy way. Usually you end up in the following way: + + private static final Set COUNTRIES = new HashSet(); + static { + validCodes.add("DENMARK"); + validCodes.add("SWEDEN"); + validCodes.add("FINLAND"); + } + + // But there's a nifty way to achive the same thing in an + // easier way, buy using something that is called Double Brace + // Initialization. + + private static final Set COUNTRIES = HashSet() {{ + add("DENMARK"); + add("SWEDEN"); + add("FINLAND"); + }} + + // The first brace is creating an new AnonymousInnerClass and the + // second one declares and instance initializer block. This block + // is called with the anonymous inner class is created. + // This does not only work for Collections, it works for all + // non-final classes. } // End main method } // End LearnJava class -- cgit v1.2.3 From 9b0877f7ebb7a73deed0c6aea40102f4abec586d Mon Sep 17 00:00:00 2001 From: Levi Bostian Date: Tue, 6 Oct 2015 09:36:03 -0500 Subject: Update java en file to fix small typo `buy` to `by` --- java.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'java.html.markdown') diff --git a/java.html.markdown b/java.html.markdown index b4757962..478ec683 100644 --- a/java.html.markdown +++ b/java.html.markdown @@ -338,7 +338,7 @@ public class LearnJava { } // But there's a nifty way to achive the same thing in an - // easier way, buy using something that is called Double Brace + // easier way, by using something that is called Double Brace // Initialization. private static final Set COUNTRIES = HashSet() {{ -- cgit v1.2.3