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//This is for beginners! ~Sinatra
//To learn more visit ->
001 // Here I'm defining a new class (Blueprint) named HelloWorld
002 // public tells Java that this should be available to all other classes
003 // classes are blue prints used to design objects that contain attributes (variables) and methods (functions)
004 // HelloWorld is just what you named your program. That allows you to reference it later
005 // { is the opening brace that surrounds the code used by HelloWorld
006 public class HelloWorld
007 {
008 // public allows other classes to use this function
009 // static means that only a class can call for this function to execute
010 // void states that this function doesn't return any values after it is done executing
011 // main is required in every Java program. This function is always executed first
012 // Every main function must accept an array of string objects
013
014 // Class variables must start with static if you want to access them with any other methods in the class
015 static String randomString = "String to print";
016
017 // Constant variables are defined with the word final
018 static final double PINUM = 3.1415929;
019
020 public static void main(String[] args)
021 {
022 // System.out is an object that outputs information
023 // println is a function that prints to the screen what ever you provide between braces
024 // "Hello World" is a string of characters. Strings must be surrounded with quotes
025 // Every statement ends with a semicolon ;
026 System.out.println("Hello World");
027
028 // Variable names are case sensitive. Age is not the same as age.
029 // Variables must begin with a letter and contain numbers, _, or $
030 // You must declare all variables before you can use them with a data type
031
032 /* You can use any variable name except for
033 * abstract continue for new switch assert default goto package synchronized
034 * boolean do if private this break double implements protected throw
035 * byte else import public throws case enum instanceof return transient
036 * catch extends int short try char final interface static void
037 * class finally long strictfp volatile const float native super while
038 */
039
040 // This is a declaration statement
041 // integerOne is a local variable to the main function. It can only be accessed in main
042 int integerOne = 22;
043
044 int integerTwo = integerOne + 1; // This is an expression statement
045
046 // White space has no meaning in Java, aside from variables and keywords
047 integerTwo =
048 integerOne
049 + 3;
050
051 System.out.println(integerTwo);
052
053 // Javas Primitive Types
054
055 byte bigByte = 127; // Minimum value -128 Maximum value 127
056 short bigShort = 32767; // Minimum value -32768 Maximum value 32767
057 int bigInt = 2147483647; // Minimum value -2147483648 Maximum value 2147483647
058 long bigLong = 9223372036854775807L; // Minimum value -9223372036854775808L
059
060 float bigFloat = 3.14F; // You must end a float with an F
061 double bigDouble = 3.1234567890D; // The D is not required with doubles
062 System.out.println(Float.MAX_VALUE); // Float is precise to 6 decimal places
063 System.out.println(Double.MAX_VALUE); // Double is precise to 15 decimal places
064
065 boolean trueOrFalse = true; // Booleans are True or False, not 1 or 0
066
067 // A char will accept a number or a character surrounded by apostrophes
068 char randomChar = 65; // Character Code for A is 65 Minimum value 0 Maximum value 65535
069 char anotherChar = 'A';
070 System.out.println(randomChar);
071
072 // chars can also contain escaped characters
073 char backSpace = '\b';
074 char formFeed = '\f';
075 char lineFeed = '\n';
076 char carriageReturn = '\r';
077 char horizontalTab = '\t';
078 char doubleQuote = '\"';
079 char singleQuote = '\'';
080 char backSlash = '\\';
081
082 // A string contains a series of characters
083 String randomString = "I'm just a random";
084 String anotherString = "string";
085
086 // You combine strings with a +
087 String combinedString = randomString + ' ' + anotherString;
088 System.out.println(combinedString);
089
090 // How to convert any other type to a string
091 String byteString = Byte.toString(bigByte);
092 String shortString = Short.toString(bigShort);
093 String intString = Integer.toString(bigInt);
094 String longString = Long.toString(bigLong);
095 String floatString = Float.toString(bigFloat);
096 String doubleString = Double.toString(bigDouble);
097 String booleanString = Boolean.toString(trueOrFalse);
098 String charString = Character.toString(randomChar); // You don't need to do this
099
100 System.out.println(charString);
101
102 // Can't do this because char is a primitive data type
103 // System.out.println(randomChar.getClass());
104
105 // You can do this because String is an object
106 System.out.println(charString.getClass());
107
108 // You use casting to convert from one primitive type to another
109 // If you convert from a number that is to big the largest possible value will be
110 // used instead
111 double aDoubleValue = 3.1456789;
112 int doubleToInt = (int) aDoubleValue;
113 System.out.println(doubleToInt);
114
115 /* To cast to other primitive types just proceed with the conversion to type
116 * ie (byte) (short) (long) (double)
117 * (float) & (boolean) & (char) don't work.
118 * (char) stays as a number instead of a character
119 */
120
121 // Use parseInt to convert a string into an integer
122 int stringToInt = Integer.parseInt(intString);
123
124 /* Other parse functions
125 * parseShort, parseLong, parseByte, parseFloat, parseDouble, parseBoolean
126 * There is no reason to parse a Character
127 */
128
129 }
130 // You must provide a closing brace } so Java knows when the function has ended
131 }
- See more at: http://www.newthinktank.com/2011/12/java-video-tutorial/#sthash.MG1HkVVc.dpuf
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http://osbot.org/forum/topic/93448-guide-simple-guide-about-navigating-through-the-apis-documentation/
