CSC 313 Java Chapter 2 continued Operators Notes to accompany Beginning Java 2 by Ivor Horton

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CSC 313 JavaChapter 2 continued Operators
Notes to accompany Beginning Java 2 by Ivor Horton
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Relational operators

• Standard relational operators for comparing
  values, return in true or false gt greater
  than lt less than gt greater than or
  equal to lt less than or equal to
  equals ! and not equals
• The equality operator should be used with caution
  on floating-point values and object references.

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Logical Operators

• Java has the standard logical operators and
• inclusive-or ! not
• Evaluation of a logical-and expression terminates
  with a value of false at the first false
  subexpression.
• Evaluation of a logical-or expression terminates
  with a value of true at the first true
  subexpression.

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Logical Operators

• Logical expressions evaluate left to right.
• The bit operators and behave as logical
  operators if their operands are booleans instead
  of integers.

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Bitwise Operations

• You can combine integer values by logically
  combining or operating on their bits using the
  bitwise operators.
• Four bitwise operators are available to work on
  integers
• Bitwise AND Bitwise OR
• Bitwise XOR Bitwise complement

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Bitwise Operations Illustrated
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Bitwise Operations Illustrated
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Shift Operators

• Java has three shift operators
• ltlt Shift left, filling with zeros from the right
• gtgt Shift right, propagating the sign bit from
  the left
• gtgtgt Shift right, filling with zeros from the left

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Shift Operators Illustrated
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Shift Operators Illustrated
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Shift Operators Illustrated
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op Operators

• shortcut addition, given X 4 X 5
  // X equals 9
• - shortcut subtraction, given X 4 X - 2
  // X equals 2
• shortcut multiplication, X4 X - 3 // X
  equals 12
• / shortcut division, X4 X / 2 // X equals 2

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instanceof operator

• This operator tests whether an object
  instantiates a class. Illustrated by this code
  segment
• Date d new Date()
• if ( d instanceof Object ) // false
• ...
• else if ( d instanceof Date ) // true
• ...

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Operator Precedence
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Operator Precedence
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Program Comments

• Java supports 3 ways of including comments line
  comments, block comments and documentation
  comments.
• // line comment, rest of line ignored by
  compiler
• / .. / block comments, all text between /
  and / ignored by compiler.
• /
• This is a documentation comment.
• /

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Program Comments

• Documentation Comments
• /
• This is a documentation comment.
• /
• Any asterisks at the beginning of each line in a
  documentation comment are ignored, as are any
  spaces
• preceding the first .
• A documentation comment can also include HTML
  tags, as well as special tags beginning with _at_
  that
• are used to document methods and classes in a
  standard form. The _at_ is followed by a keyword
  that
• defines the purpose of the tag.

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Documentation Comments
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Time to wake up.
Have a Nice Weekend!!