• Definitions:
  • An operator is a symbol indicating that an operation is to be performed on one or more operands
  • An operand can be a variable, literal, or expression
• Number of Operands:
  • A unary operator has one operand
  • A binary operator has two operands
• Boolean Values:
  • Either true (T) or false (F)

• Infix Notation for Binary Operators:
  • Operand Operator Operand
• Postfix Notation for Binary Operators:
  • Operand Operand Operator
• Prefix Notation for Binary Operators:
  • Operator Operand Operand

• Other Names:
  • Prefix Notation is sometimes called Polish Notation
  • Postfix Notation is sometimes called Reverse Polish Notation
• Resulting Humor(?):
  • 
    (Courtesy of xkcd)

• Operands:
  • Booleans
• Result:
  • A Boolean
• Unary Operations:
  • NOT - The result is the other possible value
• Binary Operations:
  • AND - The result is true if both operands are true; otherwise the result is false
  • OR - The result is false if both operands are false; otherwise the result is true
  • XOR - The result is true if the operands are different; otherwise the results is false

• Recall:
  • boolean is an atomic/primitive/fundamental type
• Literals:
  • true
  • false

• Binary Operators:
  • AND: &
  • OR: |
  • XOR: ^
• Unary Operators:
  • NOT: !

// Declare a boolean variable named ok
boolean   ok;

// Assign the value true to ok
ok = true;

• Involving Literals:
  • true & true
  • true | false
  • !false
  • true | (false & true)
• Involving Variables (Declared Elsewhere):
  • enrolled & paid
  • student | professor
  • !old

• Some Observations:
  • If the left-side operand of AND is false then the result must be false (regardless of the right-side operand)
  • If the left-side operand of OR is true then the result must be true (regardless of the right-side operand)
• An Implication:
  • It is not always necessary to evaluate the right-side operand of a logical operator

• The Short-Circuiting Operators in Java:
  • AND: &&
  • OR: ||
• Short-Circuiting in Java:
  • false && x evaluates to false (sometimes called the simplification rule) so x isn't evaluated
  • true || x evaluates to true (sometimes called the addition rule) so x isn't evaluated
• Common Practice:
  • The short-circuiting versions are almost always used

• Will the right-side operand be evaluated in the following expressions?
  • (true) || (false && true)
  • (false) || (false && true)
  • (true) && (false && true)
  • (false) && (false && true)
• Will the right-most operand be evaluated in the following expressions?
  • (true && true) || (false && true)
  • (false && true) || (false && true)
  • (true || true) && (false && true)
  • (false || true) && (false && true)

• Question:
  • Why doesn't Java have a ^^ operator?
• The (Hopefully Obvious) Answer:
  • XOR can't be short-circuited; the right-side operand must be evaluated