for InterView one question per day

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1:What's the difference between Interface and Abstract Class?
Answer:
i.similarity:
a)can not be instance
ii.Difference：
a) InterFace want to show the "like a " relation
b) Abstarct Class want to show the "is a" relation

2.Public/Private/Protected/Default?
Answer:
the difference is about the "access authority  "

pubilc:the largest access authority
private:can be access or visible by itself
protected:can be access or visible by the subclasses or the other classes in same package
default:can be ... in same package

3.the distinction  of "==" and "equals"