Difference between revisions of "Misc"

From Suhrid.net Wiki
Jump to navigationJump to search
Line 17: Line 17:
 
* String $;
 
* String $;
  
Literals
+
== Literals ==
  
 
* Default type of an integer literal is int.
 
* Default type of an integer literal is int.
Line 36: Line 36:
 
* Float is denoted by suffix f or F
 
* Float is denoted by suffix f or F
  
Comments
+
* Integers are stored in 2 complements's notation
 +
* Leftmost bit is the sign bit, the remaining bits are used to store the value
 +
* Byte - 1 byte = 8 bits.
 +
* Leftmost bit is to store the sign. So 7 bits are available for the value, so 2^7 = 128 values
 +
* Negative range is -128 to -1 (128 numbers)
 +
* Positive range is 0 to 127 (128 numbers, 0 is stored as a positive number)
 +
* So a byte can store
 +
<math>
 +
-2^7 to 2^7
 +
</math>
 +
 +
 
 +
<u> Comments </u>
 
* Comment start sequences like //, /*. /** are ignored within comment blocks.
 
* Comment start sequences like //, /*. /** are ignored within comment blocks.
 
* So trying to nest multiple-line comments will result in an error
 
* So trying to nest multiple-line comments will result in an error

Revision as of 00:29, 21 June 2011

This covers Objective 1.3

Legal Identifiers

  • Can be composed of characters, numbers, currency-symbols and connecting chars such as underscore.
  • Definition of characters are interpreted according to the charset.
  • NO special chars such as #, :, ;, @, -, etc...
  • Must start with letter, currency char, underscore but CANNOT start with a digit !
  • Java identifiers are case-sensitive.

Illegal identifiers:

  • int 23age;
  • String em@iladd;
  • List all-accounts;

These are legal!:

  • int __;
  • String $;

Literals

  • Default type of an integer literal is int.
  • Long can be specified by adding l or L
  • Octal prefix with 0
  • Hex prefix with 0x or 0X


  • Floating point literals default type is double.
float pi = 3.14; // This will be a compiler error, because 3.14 is a fp literal which is double by default
double pi = 3.14; //OK
float pi = 3.14f; //OK
  • Double can also be explicitly by adding the suffix d or D
  • Float is denoted by suffix f or F
  • Integers are stored in 2 complements's notation
  • Leftmost bit is the sign bit, the remaining bits are used to store the value
  • Byte - 1 byte = 8 bits.
  • Leftmost bit is to store the sign. So 7 bits are available for the value, so 2^7 = 128 values
  • Negative range is -128 to -1 (128 numbers)
  • Positive range is 0 to 127 (128 numbers, 0 is stored as a positive number)
  • So a byte can store

<math> -2^7 to 2^7 </math>


Comments

  • Comment start sequences like //, /*. /** are ignored within comment blocks.
  • So trying to nest multiple-line comments will result in an error
/* This is the foo algorithm
   /* which takes foo's and sort's bars */
*/