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Adam 2013-07-01 15:50:18 -07:00
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@ -24,311 +24,324 @@ import java.util.ArrayList;
// Import all classes inside of java.lang package // Import all classes inside of java.lang package
import java.security.*; import java.security.*;
// Inside of the LearnJava class, is your program's // Each .java file contains one public class, with the same name as the file.
// starting point. The main method. public class LearnJava {
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);
/////////////////////////////////////// // A program must have a main method as an entry point
// Types public static void main (String[] args) {
///////////////////////////////////////
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 // Use System.out.println to print lines
// (-32,768 <= short <= 32,767) System.out.println("Hello World!");
short fooShort = 10000; System.out.println("Integer: " + 10 + " Double: " + 3.14 + " Boolean: " + true);
// Integer - 32-bit signed two's complement integer // To print without a newline, use System.out.print
// (-2,147,483,648 <= int <= 2,147,483,647) System.out.print("Hello ");
int fooInt = 1; System.out.print("World");
// 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
*/
// 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");
}
// 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 // Types & Variables
/////////////////////////////////////// ///////////////////////////////////////
// Read about the class, and function syntax before // Declare a variable using <type> <name> [
// reading this. // Byte - 8-bit signed two's complement integer
System.out.println("\n->Classes & Functions"); // (-128 <= byte <= 127)
// Call bicycle's constructor byte fooByte = 100;
Bicycle trek = new Bicycle();
// Manipulate your object
trek.speedUp(3);
trek.setCadence(100);
System.out.println("trek info: "+trek.toString());
// Classes Syntax: // Short - 16-bit signed two's complement integer
// <public/private/protected> class <class name>{ // (-32,768 <= short <= 32,767)
// //data fields, constructors, functions all inside short fooShort = 10000;
// }
// 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 // Integer - 32-bit signed two's complement integer
} // (-2,147,483,648 <= int <= 2,147,483,647)
// The static field is only required because this class int fooInt = 1;
// is nested inside of the learnjava.java class.
public static class Bicycle {
// Bicycle's Fields/Variables // Long - 64-bit signed two's complement integer
public int cadence; // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
public int gear; long fooLong = 100000L;
public int speed;
// Constructors are a way of creating classes // (Java has no unsigned types)
// This is a default constructor
public Bicycle(){ // Float - Single-precision 32-bit IEEE 754 Floating Point
gear = 1; float fooFloat = 234.5f;
cadence = 50;
speed = 5; // 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");
} }
// This is a specified constructor (it contains arguments) // While loop
public Bicycle(int startCadence, int startSpeed, int startGear) { int fooWhile = 0;
gear = startGear; while(fooWhile < 100)
cadence = startCadence; {
speed = startSpeed; //System.out.println(fooWhile);
//Increment the counter
//Iterated 99 times, fooWhile 0->99
fooWhile++;
} }
System.out.println("fooWhile Value: " + fooWhile);
// the Bicycle class has // Do While Loop
// four functions/methods int fooDoWhile = 0;
public void setCadence(int newValue) { do
cadence = newValue; {
} //System.out.println(fooDoWhile);
//Increment the counter
//Iterated 99 times, fooDoWhile 0->99
fooDoWhile++;
}while(fooDoWhile < 100);
System.out.println("fooDoWhile Value: " + fooDoWhile);
public void setGear(int newValue) { // For Loop
gear = newValue; 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
} }
System.out.println("fooFor Value: " + fooFor);
public void applyBrake(int decrement) { // Switch Case
speed -= decrement; 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;
} }
System.out.println("Switch Case Result: " + monthString);
public void speedUp(int increment) {
speed += increment; ///////////////////////////////////////
} // Converting Data Types And Typcasting
///////////////////////////////////////
public String toString(){
return "gear: "+Integer.toString(gear)+ // Converting data
" cadence: "+Integer.toString(cadence)+
" speed: "+Integer.toString(speed); // Convert String To Integer
} Integer.parseInt("123");//returns an integer version of "123"
// bracket to close nested Bicycle class
// 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;
} }
// bracket to close learnjava.java
// This is a specified constructor (it contains arguments)
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
// 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;
}
} }
``` ```