Java OCA OCP Practice Question 3115

Question

Which one of the following definitions of the AResource class implementation is correct so that it can be used with try-with-resources statement? 

a) class AResource implements Closeable {
        protected void close() /* throws IOException */ {
            // body of close to release the resource
        }/*ww  w  . j a v  a 2s  . com*/
    }

b) class AResource implements Closeable {
        public void autoClose() /* throws IOException */ {
            // body of close to release the resource
        }
    }

c) class AResource implements AutoCloseable {
        void close() /* throws IOException */ {
             // body of close to release the resource
        }
    }

d) class AResource implements AutoCloseable {
        public void close() throws IOException {
             // body of close to release the resource
        }
    }



d)

Note

AutoCloseable is the base interface of the Closeable interface; AutoCloseable declares close as void close() throws Exception; In Closeable, it is declared as public void close() throws IOException;.

For a class to be used with try-with-resources, it should both implement Closeable or AutoCloseable and correctly override the close() method.

option a) declares close() protected; since the close() method is declared public in the base interface, you cannot reduce its visibility to protected, so this will result in a compiler error.

option b) declares autoClose(); a correct implementation would define the close() method.

option c) declares close() with default access; since the close method is declared public in the base interface, you cannot reduce its visibility to default accesses, so it will result in a compiler error.

option d) is a correct implementation of the AResource class that overrides the close() method.




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