Oracle 1Z0-816 問題集

質問 1：
Given this enum declaration:

Examine this code:
System.out.println(Alphabet.getFirstLetter());
What code should be written at line 3 to make this code print A?
A. static String getFirstLetter() { return A.toString(); }
B. static String getFirstLetter() { return Alphabet.values()[1].toString(); }
C. final String getFirstLetter() { return A.toString(); }
D. String getFirstLetter() { return A.toString(); }
正解：A

質問 2：
Given:

Which is true?
A. System.out is the standard output stream. The stream is open only when System.out is called.
B. System.in cannot reassign the other stream.
C. System.in is the standard input stream. The stream is already open.
D. System.out is an instance of java.io.OutputStream by default.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 3：
Which code is correct?
A. Runnable r = {System.out.println("Message")};
B. Runnable r = "Message" -> System.out.println();
C. Runnable r = () -> System.out::print;
D. Runnable r = -> System.out.println("Message");
E. Runnable r = () -> {System.out.println("Message");};
正解：E
解説: (Topexam メンバーにのみ表示されます)

質問 4：
Given:

What is the result?
A. 3 5 3 5
B. 3 5 3 3
C. 5 5 3 3
D. 3 3 3 3
正解：B
解説: (Topexam メンバーにのみ表示されます)

質問 5：
Which statement about a functional interface is true?
A. It cannot have any private methods and static methods.
B. It is declared with a single abstract method.
C. It must be annotated with @FunctionalInterface.
D. It is declared with a single default method.
E. It must be defined with the public access modifier.
正解：B
解説: (Topexam メンバーにのみ表示されます)

質問 6：
Which three annotation uses are valid? (Choose three.)
A. Function<String, String> func = (@NonNull x) -> x.toUpperCase();
B. Function<String, String> func = (var @NonNull x) -> x.toUpperCase();
C. var myString = (@NonNull String) str;
D. Function<String, String> func = (@NonNull var x) -> x.toUpperCase();
E. var obj = new @Interned MyObject();
F. var v = "Hello" + (@Interned) "World"
正解：A,B,E

質問 7：
Given:

When run and all three files exist, what is the state of each reader on Line 1?
A. All three readers have been closed.
B. Only reader1 has been closed.
C. The compilation fails.
D. All three readers are still open.
正解：C

質問 8：
Given:
var data = new ArrayList<>();
data.add("Peter");
data.add(30);
data.add("Market Road");
data.set(1, 25);
data.remove(2);
data.set(3, 1000L);
System.out.print(data);
What is the output?
A. [Market Road, 1000]
B. [Peter, 30, Market Road]
C. An exception is thrown at run time.
D. [Peter, 25, null, 1000]
正解：C
解説: (Topexam メンバーにのみ表示されます)