extends in java [closed]

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i have make simple java program to find volume.first i have use extends then it will run but after without extends it will not run. can we also run same program without extends?

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You say you're using "extends" I presume you mean in the context of "extending a class" which is inheritance in Java. "Extending" the parent class allows your code to interact with the code you've been provided with and so is essential