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authorSean Corrales <scorrales@gmail.com>2015-10-05 09:50:44 -0500
committerSean Corrales <scorrales@gmail.com>2015-10-05 09:50:44 -0500
commitfe5157d36f4b508479edaa214e097f65e7ba26e1 (patch)
treee6a3f377ba4ed7735bbcf3c2908082b811168e9e /java.html.markdown
parenta743c831a07f5e846051b156152fe8e6ddcfb097 (diff)
parente57fb68756ec6f4242ad04c359f7796606b52a42 (diff)
Merge pull request #1 from adambard/master
Merging changes from source branch
Diffstat (limited to 'java.html.markdown')
-rw-r--r--java.html.markdown92
1 files changed, 90 insertions, 2 deletions
diff --git a/java.html.markdown b/java.html.markdown
index 928eb39f..e4234a39 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 <type> <name>
+ int fooInt;
+ // Declare multiple variables of the same type <type> <name1>, <name2>, <name3>
+ int fooInt1, fooInt2, fooInt3;
+
+ /*
+ * Variable Initialization
+ */
+
+ // Initialize a variable using <type> <name> = <val>
+ int fooInt = 1;
+ // Initialize multiple variables of same type with same value <type> <name1>, <name2>, <name3> = <val>
+ int fooInt1, fooInt2, fooInt3;
+ fooInt1 = fooInt2 = fooInt3 = 1;
+
+ /*
+ * Variable types
+ */
// Byte - 8-bit signed two's complement integer
// (-128 <= byte <= 127)
byte fooByte = 100;
@@ -451,6 +471,74 @@ public class ExampleClass extends ExampleClassParent implements InterfaceOne,
public void InterfaceTwoMethod() {
}
}
+
+
+// Abstract Classes
+// Abstract Class declaration syntax
+// <access-level> abstract <abstract-class-name> extends <super-abstract-classes> {
+// // 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 initialize, however in an interface
+ // a variable is implicitly final and hence has
+ // to be initialized.
+ 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