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Composition and Inheritance

 
Mathews P Srampikal
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What is the difference between Composition and Inheritance in java.
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Ernest Friedman-Hill
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In Java, or in any language, inheritance is, well, inheritance -- as expressed by the "extends" keyword; while composition refers to the inclusion of one object inside another as a member.
In this example, Bar gets access to Foo's capabilites via inheritance:

While here it gets them via composition:

The general, oversimplified rule is to use composition when you can, inheritance when you must.
 
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