[所有分類]墨爾本大學(xué)java課程課件chap-在線瀏覽
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【正文】 rson AddisonWesley. All rights reserved. Abstract Classes Implementing Interfaces ? Abstract classes may implement one or more interfaces – Any method headings given in the interface that are not given definitions are made into abstract methods ? A concrete class must give definitions for all the method headings given in the abstract class and the interface 139 Copyright 169。 2021 Pearson AddisonWesley. All rights reserved. Derived Interfaces ? Like classes, an interface may be derived from a base interface – This is called extending the interface – The derived interface must include the phrase extends BaseInterfaceName ? A concrete class that implements a derived interface must have definitions for any methods in the derived interface as well as any methods in the base interface 1311 Copyright 169。 2021 Pearson AddisonWesley. All rights reserved. Pitfall: Interface Semantics Are Not Enforced ? When a class implements an interface, the piler and runtime system check the syntax of the interface and its implementation – However, neither checks that the body of an interface is consistent with its intended meaning ? Required semantics for an interface are normally added to the documentation for an interface – It then bees the responsibility of each programmer implementing the interface to follow the semantics ? If the method body does not satisfy the specified semantics, then software written for classes that implement the interface may not work correctly 1313 Copyright 169。 2021 Pearson AddisonWesley. All rights reserved. The Comparable Interface ? The Comparable interface is in the package, and so is automatically available to any program ? It has only the following method heading that must be implemented: public int pareTo(Object other)。s responsibility to follow the semantics of the Comparable interface when implementing it 1315 Copyright 169。 2021 Pearson AddisonWesley. All rights reserved. The Comparable Interface Semantics ? Almost any reasonable notion of es before is acceptable – In particular, all of the standard lessthan relations on numbers and lexicographic ordering on strings are suitable ? The relationship es after is just the reverse of es before 1317 Copyright 169。 2021 Pearson AddisonWesley. All rights reserved. Using the Comparable Interface ? The foll
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