Logical Operations

• A logical expression is an expression that evaluates to either true or false.
  
• In Java, the data type to use is the boolean data type.
• Unlike C and C++, false is false and true is true. 0 is NOT false and 1 is NOT true! If you do not know what I mean - PERFECT!
  
  
• Relational operators are used in logical expressions and only work the way you expect for primitives and references. For instance:

  >   means greater-than (only for primitives)
  <    means less-than  (only for primitives)
  >=   means greater-than-or-equal (only for primitives)
  <=   means less-than-or-equal (only for primitives)
  
  !=  means not-equal (primitives and references)
  ==  means equal (primitives and references)
      NOTE:   That's 2 equal signs in a row, with no whitespace between them.
  

*** Remember, to compare objects, you will use method calls, NOT relational operators. Look at the String class documentation to get an idea.

• Logical operators are used to make compound logical expressions. For instance:

  !   means not
  &&  means and
  ||  means or
  ^   means eor (exclusive or)
  

• Parenthesis are used for grouping logical expressions.
• Lexicographic order refers to the order in which string comparisons are done. When comparing strings, alphabetical ordering is used, with a slight twist. Digits (0-9) come first in the alphabet, then capital letters, then lower case letters.

  So, "APPLE" is less than "apple", and "apple" is less than "zoo".

• Examples:

  Logical Expression                   Evaluates to True When
  (num1 != 0)                          num1 not-equal to 0
  ((num1 == 0) && (num2 != 0))         num1 equals 0 AND num2 not-equal to 0
  ((num1 == 0) || (num2 != 0))         num1 equals 0 OR num2 not-equal to 0 (either can be true)
  ((num1 == 0) ^ (num2 != 0))          num1 equals 0 EOR num2 not-equal to 0 (only one can be true)