OCJP Study 20

OCJP(Java 6) 기출문제 연습 20(191~200)

PC나 스마트폰에서도 동일하게 실행되므로 장소를 가리지 않고 OCJP(JAVA 6) 국제 자격증을 목표로 학습할 수 있다.

QUESTION 191
Given:
class Alpha {
public void foo() { System.out.print("Afoo "); }
}
public class Beta extends Alpha {
public void foo() { System.out.print("Bfoo "); }
public static void main(String[] args) {
Alpha a = new Beta();
Beta b = (Beta)a;
a.foo();
b.foo();
}
}
What is the result?

A. Afoo Afoo
B. Afoo Bfoo
C. Bfoo Afoo
D. Bfoo Bfoo
E. Compilation fails.
F. An exception is thrown at runtime.

D

설명없음

QUESTION 191
Given:
1. public class TestOne {
2. public static void main (String[] args) throws Exception {
3. Thread.sleep(3000);
4. System.out.println("sleep");
5. }
6. }
What is the result?

A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes normally and prints "sleep".
D. The code executes normally, but nothing is printed.

C

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QUESTION 193
Given:
1. public class Threads3 implements Runnable {
2. public void run() {
3. System.out.print("running");
4. }
5. public static void main(String[] args) {
6. Thread t = new Thread(new Threads3());
7. t.run();
8. t.run();
9. t.start();
10. }
11.}
What is the result?

A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes and prints "running".
D. The code executes and prints "runningrunning".
E. The code executes and prints "runningrunningrunning".

E

설명없음

QUESTION 194
Given:
public class NamedCounter {
private final String name;
private int count;
public NamedCounter(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void increment() {
count++;
}
public int getCount() {
return count;
}
public void reset() {
count = 0;
}
}
Which three changes should be made to adapt this class to be used safely by multiple threads? (Choose three.)

A. declare reset() using the synchronized keyword
B. declare getName() using the synchronized keyword
C. declare getCount() using the synchronized keyword
D. declare the constructor using the synchronized keyword
E. declare increment() using the synchronized keyword

A,C,E

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QUESTION 195
Given that Triangle implements Runnable, and:
void go() throws Exception {
Thread t = new Thread(new Triangle());
t.start();
for(int x = 1; x < 100000; x++) {
//insert code here Linea 35
if(x%100 == 0) System.out.print("g");
}
}
public void run() {
try {
for(int x = 1; x < 100000; x++) {
// insert the same code here Linea 41
if(x%100 == 0) System.out.print("t");
}
} catch (Exception e) {
}
}
Which two statements, inserted independently at both lines 35 and 41, tend to allow both threads to temporarily pause and allow the other thread to execute? (Choose two.)

A. Thread.wait();
B. Thread.join();
C. Thread.yield();
D. Thread.sleep(1);
E. Thread.notify();

C,D

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QUESTION 196
Given:
1. public class TestSeven extends Thread {
2. private static int x;
3. public synchronized void doThings() {
4. int current = x;
5. current++;
6. x = current;
7. }
8. public void run() {
9. doThings();
10. }
11.}
Which statement is true?

A. Compilation fails.
B. An exception is thrown at runtime.
C. Synchronizing the run() method would make the class thread-safe.
D. The data in variable "x" are protected from concurrent access problems.
E. Declaring the doThings() method as static would make the class thread-safe.
F. Wrapping the statements within doThings() in a synchronized(new Object()) { } block would make the class thread-safe.

E

설명없음

QUESTION 197
Given:
public class Yikes {
public static void go(Long n) {
System.out.print("Long ");
}
public static void go(Short n) {
System.out.print("Short ");
}
public static void go(int n) {
System.out.print("int ");
}
public static void main(String[] args) {
short y = 6;
long z = 7;
go(y);
go(z);
}
}
What is the result?

A. int Long
B. Short Long
C. Compilation fails.
D. An exception is thrown at runtime.

A

설명없음

QUESTION 198
Given:
12. Date date = new Date();
13. df.setLocale(Locale.ITALY);
14. String s = df.format(date);
The variable df is an object of type DateFormat that has been initialized in line 11.
What is the result if this code is run on December 14, 2000?

A. The value of s is 14-dic-2000.
B. The value of s is Dec 14, 2000.
C. An exception is thrown at runtime.
D. Compilation fails because of an error in line 13.

D

The method setLocale(Locale) is undefined for the type DateFormat

QUESTION 199
Which two scenarios are NOT safe to replace a StringBuffer object with a StringBuilder object? (Choose two.)

A. When using versions of Java technology earlier than 5.0.
B. When sharing a StringBuffer among multiple threads.
C. When using the java.io class StringBufferInputStream.
D. When you plan to reuse the StringBuffer to build more than one string.

A,B

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QUESTION 200
Given that c is a reference to a valid java.io.Console object, and:
11. String pw = c.readPassword("%s", "pw: ");
12. System.out.println("got " + pw);
13. String name = c.readLine("%s", "name: ");
14. System.out.println(" got ", name);
If the user types fido when prompted for a password, and then responds bob when prompted for a name,
what is the result?

A. pw: got fido name: bob got bob
B. pw: fido got fido name: bob got bob
C. pw: got fido name: bob got bob
D. pw: fido got fido name: bob got bob
E. Compilation fails.
F. An exception is thrown at runtime.

E

The method println(String) in the type PrintStream is not applicable for the arguments
(String, String)