This week's book giveaway is in the Performance forum. We're giving away four copies of The Java Performance Companion and have Charlie Hunt, Monica Beckwith, Poonam Parhar, & Bengt Rutisson on-line! See this thread for details.
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;???
posted 16 years ago
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 ;