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Three
relationships are common between classes:
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Use
or awareness
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Creating/using
objects of another class, passing objects of another
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class
as arguments
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Minimize
the number of these relationships
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One
class should be as unaware as possible of the existence of
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another
class! Eases future modification!
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Aggregation
or containment
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has
a relationship, a special case of usage
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One
object contains another object (a rectangle has 4 points)
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Inheritance
or specialization
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is
a relationship ( a rectangle is a polygon)
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Can
lead to very powerful designs
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