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answer please

 
josephine chen
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given classes MyBase and MySub such that MySub is a subclass of MyBase, which line(s) if any cause a compiler error? Which line(s) if any cause a ClassCastException...
1. MyBase objBase = new MyBase(); ok
2. MySub objSub = new MySub(); ok
3. objBase = objSub; ok
4. objSub = obj ??? consider obj is a object of class Object
5. objBase = (MyBase)objSub;??
6. objSub = (MySub)objBase;???
 
Anonymous
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Only line 4 causes compilation error, the rest of the lines are correct. Explicit cast is needed at line 4.
The line 4 could be modified as
objSub =(MySub) obj ;
 
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