Why we use interface as main concept in Java? -

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can please provide me best use of interface, because further complete reading have not found proves why use interface.

i have read interface not found solution why interface used. please explain me examples.

the principle of interface simple: contract.

an interface documented; methods of interface 1 thing , well, , implementations ensure contract fulfilled.

for instance, let take simple interface, iterator. have collections.emptyiterator() fulfills interface. whatever class x, can declare:

final iterator<x> iterator = collections.emptyiterator();

you guaranteed particular implementation correctly implement next(), .hasnext() , .remove() methods.

similarly, if have list<x> , do:

final iterator<x> iterator = list.iterator();

you guaranteed same.

accessing through interfaces allow tell users contract should use particular method of yours. implementation does not matter, , key here.

Brazzel