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Added file name param and more. See description.

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-Fixed some minor issues/details
-Can actually compile now (not just a bunch of random snippets)
-Added more text & explanation to a few parts
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Jake Prather 2013-06-30 12:17:19 -05:00
parent 35a27a3337
commit fbe0fb4718
1 changed files with 201 additions and 178 deletions
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java.html.markdown
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@ -6,6 +6,8 @@ author: Jake Prather
author_url: http://github.com/JakeHP author_url: http://github.com/JakeHP
filename: learnjava.java
--- ---
Java is a general-purpose, concurrent, class-based, object-oriented computer programming language. Java is a general-purpose, concurrent, class-based, object-oriented computer programming language.
@ -19,120 +21,120 @@ Multi-line comments look like this.
// Import Packages // Import Packages
import java.util.ArrayList; import java.util.ArrayList;
import package.path.here;
// Import all "sub-packages" // Import all "sub-packages"
import java.lang.Math.*; import java.lang.Math.*;
// Your program's entry point is a function called main // Inside of the learnjava class, is your program's
public class Main // starting point. The main method.
public class learnjava
{ {
public static void main (String[] args) throws java.lang.Exception //main method
public static void main (String[] args)
{ {
//stuff here
} System.out.println("->Printing");
} // Printing, and forcing a new line on next print, use println()
System.out.println("Hello World!");
// Printing, and forcing a new line on next print = println() System.out.println("Integer: "+10+" Double: "+3.14+ " Boolean: "+true);
System.out.println("Hello World"); // Printing, without forcing a new line on next print, use print()
System.out.println("Integer: "+10+"Double: "+3.14+ "Boolean: "+true); System.out.print("Hello World - ");
// Printing, without forcing a new line on next print = print() System.out.print("Integer: "+10+" Double: "+3.14+ " Boolean: "+true);
System.out.print("Hello World");
System.out.print("Integer: "+10+"Double: "+3.14+ "Boolean: "+true);
/////////////////////////////////////// ///////////////////////////////////////
// Types // Types
/////////////////////////////////////// ///////////////////////////////////////
System.out.println("\n\n->Types");
// Byte - 8-bit signed two's complement integer // Byte - 8-bit signed two's complement integer
// (-128 <= byte <= 127) // (-128 <= byte <= 127)
byte foo = 100; byte fooByte = 100;
// Short - 16-bit signed two's complement integer // Short - 16-bit signed two's complement integer
// (-32,768 <= short <= 32,767) // (-32,768 <= short <= 32,767)
short bar = 10000; short fooShort = 10000;
//Integer - 32-bit signed two's complement integer // Integer - 32-bit signed two's complement integer
// (-2,147,483,648 <= int <= 2,147,483,647) // (-2,147,483,648 <= int <= 2,147,483,647)
int foo = 1; int fooInt = 1;
//Long - 64-bit signed two's complement integer // Long - 64-bit signed two's complement integer
// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807) // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
long bar = 100000L; long fooLong = 100000L;
// (Java has no unsigned types) // (Java has no unsigned types)
//Float - Single-precision 32-bit IEEE 754 Floating Point // Float - Single-precision 32-bit IEEE 754 Floating Point
float foo = 234.5f; float fooFloat = 234.5f;
//Double - Double-precision 64-bit IEEE 754 Floating Point // Double - Double-precision 64-bit IEEE 754 Floating Point
double bar = 123.4; double fooDouble = 123.4;
//Boolean - True & False // Boolean - True & False
boolean foo = true; boolean fooBoolean = true;
boolean bar = false; boolean barBoolean = false;
//Char - A single 16-bit Unicode character // Char - A single 16-bit Unicode character
char foo = 'A'; char fooChar = 'A';
//Make a variable a constant // Make a variable a constant
final int HOURS_I_WORK_PER_WEEK = 9001; final int HOURS_I_WORK_PER_WEEK = 9001;
//Strings // Strings
String foo = "Hello World!"; String fooString = "My String Is Here!";
// \n is an escaped character that starts a new line // \n is an escaped character that starts a new line
String foo = "Hello World!\nLine2!"; String barString = "Printing on a new line?\nNo Problem!";
System.out.println(foo); System.out.println(fooString);
//Hello World! System.out.println(barString);
//Line2!
//Arrays // Arrays
//The array size must be decided upon declaration //The array size must be decided upon declaration
//The format for declaring an array is follows: //The format for declaring an array is follows:
//<datatype> [] <var name> = new <datatype>[<array size>]; //<datatype> [] <var name> = new <datatype>[<array size>];
int [] array = new int[10]; int [] intArray = new int[10];
String [] array = new String[1]; String [] stringArray = new String[1];
boolean [] array = new boolean[100]; boolean [] booleanArray = new boolean[100];
// Indexing an array - Accessing an element // Indexing an array - Accessing an element
array[0]; System.out.println("intArray @ 0: "+intArray[0]);
// Arrays are mutable; it's just memory! // Arrays are mutable; it's just memory!
array[1] = 1; intArray[1] = 1;
System.out.println(array[1]); // => 1 System.out.println("intArray @ 1: "+intArray[1]); // => 1
array[1] = 2; intArray[1] = 2;
System.out.println(array[1]); // => 2 System.out.println("intArray @ 1: "+intArray[1]); // => 2
//Others to check out // Others to check out
//ArrayLists - Like arrays except more functionality is offered, // ArrayLists - Like arrays except more functionality is offered,
// and the size is mutable // and the size is mutable
//LinkedLists // LinkedLists
//Maps // Maps
//HashMaps // HashMaps
/////////////////////////////////////// ///////////////////////////////////////
// Operators // Operators
/////////////////////////////////////// ///////////////////////////////////////
System.out.println("\n->Operators");
int i1 = 1, i2 = 2; // Shorthand for multiple declarations int i1 = 1, i2 = 2; // Shorthand for multiple declarations
// Arithmetic is straightforward // Arithmetic is straightforward
i1 + i2; // => 3 System.out.println("1+2 = "+(i1 + i2)); // => 3
i2 - i1; // => 1 System.out.println("1+2 = "+(i2 - i1)); // => 1
i2 * i1; // => 2 System.out.println("1+2 = "+(i2 * i1)); // => 2
i1 / i2; // => 0 (0.5, but truncated towards 0) System.out.println("1+2 = "+(i1 / i2)); // => 0 (0.5, but truncated towards 0)
// Modulo // Modulo
11 % 3; // => 2 System.out.println("11%3 = "+(11 % 3)); // => 2
// Comparison operators // Comparison operators
3 == 2; // => 0 (false) System.out.println("3 == 2? "+(3 == 2)); // => 0 (false)
3 != 2; // => 1 (true) System.out.println("3 != 2? "+(3 != 2)); // => 1 (true)
3 > 2; // => 1 System.out.println("3 > 2? "+(3 > 2)); // => 1
3 < 2; // => 0 System.out.println("3 < 2? "+(3 < 2)); // => 0
2 <= 2; // => 1 System.out.println("2 <= 2? "+(2 <= 2)); // => 1
2 >= 2; // => 1 System.out.println("2 >= 2? "+(2 >= 2)); // => 1
// Bitwise operators! // Bitwise operators!
/*
~ Unary bitwise complement ~ Unary bitwise complement
<< Signed left shift << Signed left shift
>> Signed right shift >> Signed right shift
@ -140,100 +142,110 @@ i1 / i2; // => 0 (0.5, but truncated towards 0)
& Bitwise AND & Bitwise AND
^ Bitwise exclusive OR ^ Bitwise exclusive OR
| Bitwise inclusive OR | Bitwise inclusive OR
*/
// Incrementations // Incrementations
int i=0; int i=0;
i++; //i = 1. Post-Incrementation System.out.println("\n->Inc/Dec-rementation");
++i; //i = 2. Pre-Incrementation System.out.println(i++); //i = 1. Post-Incrementation
i--; //i = 1. Post-Decrementation System.out.println(++i); //i = 2. Pre-Incrementation
--i; //i = 0. Pre-Decrementation System.out.println(i--); //i = 1. Post-Decrementation
System.out.println(--i); //i = 0. Pre-Decrementation
/////////////////////////////////////// ///////////////////////////////////////
// Control Structures // Control Structures
/////////////////////////////////////// ///////////////////////////////////////
System.out.println("\n->Control Structures");
if (false) { if (false){
System.out.println("I never run"); System.out.println("I never run");
} else if (false) { }else if (false) {
System.out.println("I am also never run"); System.out.println("I am also never run");
} else { } else {
System.out.println("I print"); System.out.println("I print");
}
} }
// While loop // While loop
int i = 0; int fooWhile = 0;
while(i < 100){ while(fooWhile < 100)
System.out.println(i); {
//System.out.println(fooWhile);
//Increment the counter //Increment the counter
i++; //Iterated 99 times, fooWhile 0->99
fooWhile++;
} }
System.out.println("fooWhile Value: "+fooWhile);
// Do While Loop // Do While Loop
int i = 0; int fooDoWhile = 0;
do{ do
System.out.println(i); {
//System.out.println(fooDoWhile);
//Increment the counter //Increment the counter
i++; //Iterated 99 times, fooDoWhile 0->99
}while(i < 100); fooDoWhile++;
}while(fooDoWhile < 100);
System.out.println("fooDoWhile Value: "+fooDoWhile);
// For Loop // For Loop
int i; int fooFor;
//for loop structure => for(<start_statement>;<conditional>;<step>) //for loop structure => for(<start_statement>;<conditional>;<step>)
for(i=0;i<100;i++){ for(fooFor=0;fooFor<100;fooFor++){
System.out.println(i); //System.out.println(fooFor);
//Iterated 99 times, fooFor 0->99
} }
System.out.println("fooFor Value: "+fooFor);
// Switch Case // Switch Case
int month = 8; int month = 8;
String monthString; String monthString;
switch (month) { switch (month){
case 1: monthString = "January"; case 1: monthString = "January";
break; break;
case 2: monthString = "February"; case 2: monthString = "February";
break; break;
case 3: monthString = "March"; case 3: monthString = "March";
break; break;
case 4: monthString = "April"; case 4: monthString = "April";
break; break;
case 5: monthString = "May"; case 5: monthString = "May";
break; break;
case 6: monthString = "June"; case 6: monthString = "June";
break; break;
case 7: monthString = "July"; case 7: monthString = "July";
break; break;
case 8: monthString = "August"; case 8: monthString = "August";
break; break;
case 9: monthString = "September"; case 9: monthString = "September";
break; break;
case 10: monthString = "October"; case 10: monthString = "October";
break; break;
case 11: monthString = "November"; case 11: monthString = "November";
break; break;
case 12: monthString = "December"; case 12: monthString = "December";
break; break;
default: monthString = "Invalid month"; default: monthString = "Invalid month";
break; break;
} }
System.out.println(monthString); System.out.println("Switch Case Result: "+monthString);
/////////////////////////////////////// ///////////////////////////////////////
// Typecasting // Converting Data Types And Typcasting
/////////////////////////////////////// ///////////////////////////////////////
// Converting data // Converting data
//Convert String To Integer // Convert String To Integer
Integer.parseInt("123");//returns an integer version of "123" Integer.parseInt("123");//returns an integer version of "123"
//Convert Integer To String // Convert Integer To String
Integer.toString(123);//returns a string version of 123 Integer.toString(123);//returns a string version of 123
//For other conversions check out the following classes: // For other conversions check out the following classes:
//Double // Double
//Long // Long
//String // String
// Typecsating
// You can also cast java objects, there's a lot of details and // You can also cast java objects, there's a lot of details and
// deals with some more intermediate concepts. // deals with some more intermediate concepts.
// Feel free to check it out here: http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html // Feel free to check it out here: http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
@ -243,66 +255,77 @@ Integer.toString(123);//returns a string version of 123
// Classes And Functions // Classes And Functions
/////////////////////////////////////// ///////////////////////////////////////
// Classes Syntax shown below. // Read about the class, and function syntax before
// Function declaration syntax: // reading this.
// <public/private/protected> <return type> <function name>(<args>) System.out.println("\n->Classes & Functions");
// Here is a quick rundown on access level modifiers (public, private, etc.) // Call bicycle's constructor
// http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html Bicycle trek = new Bicycle();
// Manipulate your object
trek.speedUp(3);
trek.setCadence(100);
System.out.println("trek info: "+trek.toString());
// Classes Syntax:
// <public/private/protected> class <class name>{
// //data fields, constructors, functions all inside
// }
// 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
public class Bicycle { // This bracket ends the main method
// Bicycle's Fields/Variables
public int cadence;
public int gear;
public int speed;
// Constructors are a way of creating classes
// This is a default constructor
public Bicycle(){
gear = 1;
cadence = 50;
startGear = 1;
}
// This is a specified constructor (it contains arguments)
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
// the Bicycle class has
// four methods
public void setCadence(int newValue) {
cadence = newValue;
}
public void setGear(int newValue) {
gear = newValue;
}
public void applyBrake(int decrement) {
speed -= decrement;
}
public void speedUp(int increment) {
speed += increment;
}
} }
// The static field is only required because this class
// is nested inside of the learnjava.java class.
public static class Bicycle {
//Now..Later in the main / driver of your java program // Bicycle's Fields/Variables
public class Main public int cadence;
{ public int gear;
public static void main (String[] args) throws java.lang.Exception public int speed;
{
//Call bicycle's constructor // Constructors are a way of creating classes
Bicycle trek = new Bicycle(); // This is a default constructor
//Manipulate your object public Bicycle(){
trek.speedUp(3); gear = 1;
trek.setCadence(100); cadence = 50;
speed = 5;
}
// This is a specified constructor (it contains arguments)
public Bicycle(int startCadence, int startSpeed, int startGear) {
gear = startGear;
cadence = startCadence;
speed = startSpeed;
}
// the Bicycle class has
// four functions/methods
public void setCadence(int newValue) {
cadence = newValue;
}
public void setGear(int newValue) {
gear = newValue;
}
public void applyBrake(int decrement) {
speed -= decrement;
}
public void speedUp(int increment) {
speed += increment;
}
public String toString(){
return "gear: "+Integer.toString(gear)+
" cadence: "+Integer.toString(cadence)+
" speed: "+Integer.toString(speed);
}
// bracket to close nested Bicycle class
} }
// bracket to close learnjava.java
} }
``` ```