Oracle 1Z0-804 問題集

質問 1：
Which two properly implement a Singleton pattern?
A. class Singleton {
Singleton () {}
private static class SingletonHolder {
private static final Singleton INSTANCE = new Singleton ();
}
public static Singleton getInstance () {
return SingletonHolder.INSTANCE; } }
B. enum Singleton {
INSTANCE;
}
C. class Singleton {
private static Singleton instance = new Singleton();
protected Singleton () {}
public static Singleton getInstance () {
return instance;
}
}
D. class Singleton {
private static Singleton instance;
private Singleton () {}
public static synchronized Singleton getInstance() {
if (instance == null) {
instance = new Singleton ();
}
return instance;
}
}
正解：B,D
解説: (Topexam メンバーにのみ表示されます)

質問 2：
Given:

What is the result?
A. 0
B. 2
C. Compilation fails
D. 1
E. An exception is thrown at runtime
正解：E
解説: (Topexam メンバーにのみ表示されます)

質問 3：
Given: Which fragment, inserted in the Books interface, enables the code to compile?

A. public String type = "Fiction"; public abstract String getType();
B. public abstract String type; public abstract String getType();
C. public String type = "Fiction"; public static String getType();
D. public static String type; public abstract String getType();
正解：A

質問 4：
Given the code fragment: Which two try statements, when inserted at line ***, enable the code to successfully move the file info.txt to the destination directory, even if a file by the same name already exists in the destination directory?

A. try ( Files.copy(Paths.get(source), Paths.get(dest),StandardCopyOption.REPLACE_EXISTING); Files.delete
(Paths.get(source));
B. try (FileChannel in = new FileInputStream (source). getChannel(); FileChannel out = new FileOutputStream
(dest).getChannel()) { in.transferTo(0, in.size(), out);
C. try(BufferedReader br = Files.newBufferedReader(Paths.get(source), Charset.forName("UTF
8"));
BufferedWriter bw = Files.newBufferedWriter(Paths.get(dest), Charset.forName("UTF-8")); String
record =
"";
while ((record = br.readLine()) ! = null) {
bw.write(record);
bw.newLine();
} Files.delete(Paths.get(source));
D. try ( Files.copy(Paths.get(source),Paths.get(dest)); Files.delete (Paths.get(source));
E. try (Files.move(Paths.get(source),Paths.get(dest));
正解：A,C
解説: (Topexam メンバーにのみ表示されます)

質問 5：
Given:

What is the result?
A. Daniel
B. An exception is thrown at runtime.
C. Compilation fails.
D. Unknown
E. It may print"unknown"or"Daniel"depending on the JVM implementation.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 6：
Given: And the commands: javac Counter.java java ea Counter

What is the result?
A. 2
B. 3
C. Compilation fails
D. NullPointException is thrown at runtime
E. AssertionError is thrown at runtime
正解：B
解説: (Topexam メンバーにのみ表示されます)

質問 7：
For which three objects must a vendor provide implementations in its JDBC driver?
A. ResultSet
B. Statement
C. DriverManager
D. Date
E. Time
F. SQLException
G. Connection
正解：A,B,G
解説: (Topexam メンバーにのみ表示されます)

質問 8：
Given the directory structure that contains three directories: company, Salesdat, and Finance: Company
-Salesdat
* Target.dat
-Finance
*Salary.dat
*Annual.dat
And the code fragment:

If Company is the current directory, what is the result?
A. Prints at least Salesdat, Annual.dat, Salary.dat, Target.dat
B. Prints only Salesdat, Annual.dat
C. Prints only Annual.dat
D. Prints only Annual.dat, Salary.dat, Target.dat
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 9：
Given:
String s = new String("3"); System.out.print(1 + 2 + s + 4 + 5);
What is the result?
A. 1239
B. 3345
C. 12345
D. Compilation fails.
E. 339
正解：B
解説: (Topexam メンバーにのみ表示されます)