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Code Issues Projects Releases Wiki Activity

Fixed few mistakes. Added few missing features.

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1. Added JavaDoc comments.
2. Mentioned and used tab character by giving an example on escape
character for Tab.
3. Fixed the condition evaluation to true or false instead of 1 or 0.
4. Added switch case statement example for Strings.
5. Added default access level modifier to the Java class.
6. Added Java Tutorial trail to links for further research.
7. Added link for OOP Concepts for Java and have put all the
corresponding links as a children to this.
8. Fixed various other statements for consistency.
This commit is contained in:
Prashanth Babu 2013-07-07 14:38:43 +05:30
parent 2fd1664c29
commit 8245d1dda3
1 changed files with 93 additions and 38 deletions
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131
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@ -15,6 +15,9 @@ Java is a general-purpose, concurrent, class-based, object-oriented computer pro
/*
Multi-line comments look like this.
*/
/**
JavaDoc comments look like this. Used to describe the Class or various attributes of a Class.
*/
// Import ArrayList class inside of the java.util package
import java.util.ArrayList;
@ -58,12 +61,12 @@ public class LearnJava {
// 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;
long fooLong = 100000L; // L is used to denote that this variable value is of type Long; else it is treated as integer by default.
// (Java has no unsigned types)
// Note: Java has no unsigned types
// Float - Single-precision 32-bit IEEE 754 Floating Point
float fooFloat = 234.5f;
float fooFloat = 234.5f; // f is used to denote that this variable value is of type float; else it is treated as double.
// Double - Double-precision 64-bit IEEE 754 Floating Point
double fooDouble = 123.4;
@ -83,8 +86,11 @@ public class LearnJava {
// \n is an escaped character that starts a new line
String barString = "Printing on a new line?\nNo Problem!";
// \t is an escaped character that adds a tab character
String bazString = "Do you want to add a tab?\tNo Problem!";
System.out.println(fooString);
System.out.println(barString);
System.out.println(bazString);
// Arrays
//The array size must be decided upon declaration
@ -128,12 +134,12 @@ public class LearnJava {
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
System.out.println("3 == 2? " + (3 == 2)); // => false
System.out.println("3 != 2? " + (3 != 2)); // => true
System.out.println("3 > 2? " + (3 > 2)); // => true
System.out.println("3 < 2? " + (3 < 2)); // => false
System.out.println("2 <= 2? " + (2 <= 2)); // => true
System.out.println("2 >= 2? " + (2 >= 2)); // => true
// Bitwise operators!
/*
@ -144,10 +150,11 @@ public class LearnJava {
& Bitwise AND
^ Bitwise exclusive OR
| Bitwise inclusive OR
[Java Bitwise Operators](http://docs.oracle.com/javase/tutorial/java/nutsandbolts/op3.html)
*/
// Incrementations
int i=0;
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
@ -160,12 +167,13 @@ public class LearnJava {
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");
int j = 10;
if (j == 10){ // Evaluates to true only if value of j is equal to 10.
System.out.println("In this case, I get executed and I print this since j is equal to 10.");
} else if (i > 10) { // Evaluates to true only if value of j is greater than 10.
System.out.println("I never run if j = 10; I will run only if j is greater than 10");
} else { // If none of the above if-conditions match, then control will fall back to else-condition; In this case, if value of j is less than 10.
System.out.println("I also never run if j = 10; I will run only if j is less than 10");
}
// While loop
@ -200,19 +208,47 @@ public class LearnJava {
System.out.println("fooFor Value: " + fooFor);
// Switch Case
//A switch works with the byte, short, char, and int primitive data types.
//It also works with enumerated types (discussed in Enum Types), the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer.
int month = 3;
String monthString;
switch (month){
case 1: monthString = "January";
case 1:
monthString = "January";
break;
case 2: monthString = "February";
case 2:
monthString = "February";
break;
case 3: monthString = "March";
case 3:
monthString = "March";
break;
default: monthString = "Some other month";
default: //The default section handles all values that are not explicitly handled by one of the case sections.
monthString = "Some other month";
break;
}
System.out.println("Switch Case Result: " + monthString);
// Effective JDK 7.0, Strings can be used for case-matching in Switch statement.
final String dayOfWeek = "Friday";
switch (dayOfWeek) {
case "Monday":
System.out.println("Aargh!! Start of the work week!");
break;
case "Tuesday":
case "Wednesday":
case "Thursday":
System.out.println("Midweek");
break;
case "Friday":
System.out.println("Awesome! End of work week");
break;
case "Saturday":
case "Sunday":
System.out.println("Weekend");
break;
default:
System.out.println("There is no such weekday, at least on our planet.");
}
///////////////////////////////////////
@ -251,10 +287,11 @@ public class LearnJava {
Bicycle trek = new Bicycle();
// Call object methods
trek.speedUp(3);
trek.speedUp(3); // Should always use setter and getter methods to access the attributes of a class
trek.setCadence(100);
// toString is a convention
// toString is a convention to display the attribute values of this Object.
// Has to be overridden in the POJO (Plain Old Java Objects) to see the actual values else internal representation of the address will be displayed.
System.out.println("trek info: " + trek.toString());
} // End main method
@ -266,15 +303,17 @@ public class LearnJava {
// Class Declaration Syntax:
// <public/private/protected> class <class name>{
// //data fields, constructors, functions all inside
// //data fields, constructors, functions all inside.
// //functions are called as methods in Java.
// }
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
private int speed; // Private: Only accessible from within the class
protected int gear; // Protected: Accessible from the class and all the subclasses
String name; // default: Only accessible from within this package
// Constructors are a way of creating classes
// This is a default constructor
@ -282,13 +321,15 @@ class Bicycle {
gear = 1;
cadence = 50;
speed = 5;
name = "Bontrager";
}
// This is a specified constructor (it contains arguments)
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
public Bicycle(int startCadence, int startSpeed, int startGear, String name) {
this.gear = startGear;
this.cadence = startCadence;
this.speed = startSpeed;
this.name = name;
}
// Function Syntax:
@ -319,10 +360,21 @@ class Bicycle {
speed -= decrement;
}
public void setName(int newName) {
name = newName;
}
public String getName() {
return name;
}
//Method to display the attribute values of this Object.
@Override
public String toString() {
return "gear: "+Integer.toString(gear)+
" cadence: "+Integer.toString(cadence)+
" speed: "+Integer.toString(speed);
return "gear: " + gear +
" cadence: " + cadence +
" speed: " + speed +
" name: " + name;
}
} // end class Bicycle
@ -333,7 +385,7 @@ class PennyFarthing extends Bicycle {
public PennyFarthing(int startCadence, int startSpeed){
// Call the parent constructor with super
super(startCadence, startSpeed, 0);
super(startCadence, startSpeed, 0, "PennyFarthing");
}
// You should mark a method you're overriding with an @annotation
@ -350,13 +402,18 @@ class PennyFarthing extends Bicycle {
## Further Reading
The links provided here below are just to get an understanding of the topic, feel free to Google and find specific examples.
Other Topics To Research:
* [Inheritance](http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html)
* [Java Tutorial Trail from Sun / Oracle](http://docs.oracle.com/javase/tutorial/index.html)
* [Polymorphism](http://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html)
* [Java Access level modifiers](http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html)
* [Abstraction](http://docs.oracle.com/javase/tutorial/java/IandI/abstract.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)
@ -365,5 +422,3 @@ Other Topics To Research:
* [Generics](http://docs.oracle.com/javase/tutorial/java/generics/index.html)
* [Java Code Conventions](http://www.oracle.com/technetwork/java/codeconv-138413.html)
* The links provided are just to get an understanding of the topic, feel free to google and find specific examples