OCPJP Simulation Test 75

75

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Question List

Question: Given Deque<? extends FilterOutputStream> deque = new ArrayDeque<FilterOutputStream>(), what are the following code compiles?

Choice:
A. deque.add(new Object());
B. deque.add(new OutputStream());
C. deque.add(new FilterOutputStream());
D. deque.add(new BufferOutputStream());
E. deque.add(new ObjectInputStream());
F. deque.add(new PrintStream());
G. deque.add(new ObjectOutputStream());
H. none of the above



Next Question

Answer: H

Explain: You can not modify a collection declared with upper bound wildcards.

Study:  Create and use a generic class 
Use BufferedReader, BufferedWriter, File, FileReader, FileWriter, FileInputStream, FileOutputStream, ObjectOutputStream, ObjectInputStream, and PrintWriter in the java.iopackage.