OCPJP Simulation Test 77

77

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Question List

Question: Given Queue<? extends InputStream> queue = new LinkedBlockingQueue<InputStream>(), what are the following code compiles?

Choice:
A. queue.add(new InputStream());
B. queue.add(new FileInputStream());
C. queue.add(new FileReader());
D. queue.add(new BufferedInputStream());
E. queue.add(new ObjectInputStream());
F. queue.add(new OutputStream());
G. queue.add(new FilterInputStream());
H. None of the above



Next Question

Answer: H

Explain: collections declared with upper bound wildcards can not be modified.

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