Variable Types

Variable Types

Since Variables stand for items that the program is manipulating or playing with,  such as:                         whole numbers       (small  normal   large)                         fractional numbers        (small   large)                         single characters                         groups of characters as a unit                          true / false conditions  it is only logical to assume that JAVA gives the programmer  the  capability to declare and use Variables that can hold each of the above data types.  Remember that values ( or data ) being put into Variables is the heart or basis of programming.  Variables MUST be declared before they can be used in a program. Common Variable types are as follows:    short                     ... small integers    int                          ... normal integers    long                       ... big integers    float                       ... small fractional numbers    double                   ... big fractional numbers     char                       ... single character values   e.g.,     M    or   F    string                     ... groups of characters viewed as a unit    Boolean                 ... logical  TRUE  or  FALSE  values  In object oriented and more sophisticated programs today, the programmer can declare his or her own data type ( later ) Specifics concerning Java Data TYpes NUMERIC (all numbers are signed) short integer (16 bit number) --> i.e. 32,768 int integer (32 bit number) --> i.e. 2 billion or 2 x 109 long integer (64 bit number) --> i.e. 9 x 1018 float real (32 bit decimal) --> i.e. 1.4 x 10-45 to 3.4 x 1038 double real (64 bit decimal) --> i.e. 4.9 x 10-324 to 1.7 x 10308   CHARACTER / STRING char a unicode (2-byte) char the String class handles multi-character strings (strings are unicode, as well). Strings are said to be immutable: updates to a String cause the new string to be created in memory (and pointed to by the String class). However the old string is not actually "updated", rather, its reference is lost (and it becomes available for garbage collection).   BOOLEAN boolean (with values true, false)   DATE the Date class measures the milliseconds since Jan 1, 1970 and provides supporting functions to interpret and manipulate date/times   ARRAYS arrays hold multiple instances of a data type or object