Which statement is true?
(A) The time to find the value from HashMap with a Person key depends on the size of the map.
(B) Deleting a Person key from a HashMap will delete all map entries for all keys of type Person.
(C) Inserting a second Person object into a HashSet will cause the first Person object to be removed as a
duplicate.
(D) The time to determine whether a Person object is contained in a HashSet is constant and does NOT
depend on the size of the map.
A programmer iterates over the TreeSet and prints the name of each Drink object.
What is the result?
(A) Tea
(B) Coffee
(C) Coffee Tea
(D) Compilation fails.
(E) The code runs with no output.
207
A programmer must create a generic class MinMax and the type parameter of MinMax must implement
Comparable. Which implementation of MinMax will compile?
Which code, inserted at line 4, guarantees that this program will output [1, 2]?
(A) Set set = new TreeSet();
(B) Set set = new HashSet();
(C) Set set = new SortedSet();
(D) List set = new SortedList();
(E) Set set = new LinkedHashSet();
Which statement is true about the set variable on line 12?
(A) The set variable contains all six elements from the coll collection, and the order is guaranteed to be
preserved.
(B) The set variable contains only three elements from the coll collection, and the order is guaranteed to be
preserved.
(C) The set variable contains all six elements from the coll collection, but the order is NOT guaranteed to be
preserved.
(D) The set variable contains only three elements from the coll collection, but the order is NOT guaranteed
to be preserved.
What is the appropriate definition of the hashCode method in class Person?
(A) return super.hashCode();
(B) return name.hashCode() + age * 7;
(C) return name.hashCode() + comment.hashCode() / 2;
(D) return name.hashCode() + comment.hashCode() / 2- age * 3;
A programmer is developing a class Key, that will be used as a key in a standard java.util.HashMap.
Which two methods should be overridden to assure that Key works correctly as a key? (Choose two.)
(A) public int hashCode()
(B) public void hashCode()
(C) public int compareTo(Object o)
(D) public boolean equals(Object o)
(E) public boolean compareTo(Key k)
Which two code fragments, inserted independently at line 5, will compile without warnings? (Choose two.)
(A) public void addStrings(List list){
(B) public void addStrings(List＜String＞ list){
(C) public void addStrings(List＜? super String＞ list){
(D) public void addStrings(List＜? extends String＞ list){
213
Given a class whose instances, when found in a collection of objects, are sorted by using the compareTo()
method, which two statements are true? (choose two.)
(A) The class implements java.lang.Comparable.
(B) The class implements java.util.Comparator.
(C) The interface used to implement sorting allows this class to define only one sort sequence.
(D) The interface used to implement sorting allows this class to define many different sort sequences.
1. It is possible for more than two threads to deadlock at once.
2. The JVM implementation guarantees that multiple threads cannot enter into a deadlocked state.
3. Deadlocked threads release once their sleep() method's sleep duration has expired.
4. Deadlocking can occur only when the wait(), notify() and notifyAll() methods are used incorrectly.
5. It is possible for a single-threaded application to deadlock if synchronized blocks are used incorrectly.
6. If a piece of code is capable of deadlocking, you cannot eliminate the possibility of deadlocking by
inserting invocations of Thread.yield().
(A) 16
(B) 25
(C) 34
(D) 12
Which statement is true?
(A) This code can throw an InterruptedException.
(B) This code can throw an IllegalMonitorStateException.
(C) This code can throw a TimeoutException after ten minutes.
(D) Reversing the order of obj.wait() and obj.notify() might cause this method to complete normally.
(E) A call to notify() or notifyAll() from another thread might cause this method to complete normally.
(AB) This code does NOT compile unless "obj.wait()" is replaced with "((Thread) obj).wait()".
Which statement is true?
(A) The output could be 5-1 6-1 6-2 5-2
(B) The output could be 6-1 6-2 5-1 5-2
(C) The output could be 6-1 5-2 6-2 5-1
(D) The output could be 6-1 6-2 5-1 7-1
What is the result?
(A) Compilation fails.
(B) An exception is thrown at runtime.
(C) The code executes normally and prints "foo";
(D) The code executes normally, but nothing is printed.
226
Which two statements are true? (Choose two.)
(A) It is possible to synchronize static methods.
(B) When a thread has yielded as a result of yield(), it releases its locks.
(C) When a thread is sleeping as a result of sleep(), it releases its locks.
(D) The Object.wait() method can be invoked only from a synchronized context.
(E) The Thread.sleep() method can be invoked only from a synchronized context.
(AB) When the thread scheduler receives a notify() request, and notifies a thread, that thread immediately
releases its lock.
What can be a result?
(A) Compilation fails.
(B) An exception is thrown at runtime.
(C) The code executes and prints "StartedComplete".
(D) The code executes and prints "StartedComplete0123".
(E) The code executes and prints "Started0123Complete".
Which two changes, taken together, would guarantee the output: 1, 2, 3, 4, 5, ? (Choose two.)
(A) move the line 12 print statement into the foo() method
(B) change line 7 to public synchronized void go(){
(C) change the variable declaration on line 2 to private volatile int x;
(D) wrap the code inside the foo() method with a synchronized(this) block
(E) wrap the for loop code inside the go() method with a synchronized block synchronized(this){//for loop
code here}
230
Given that t1 is a reference to a live thread, which is true?
(A) The Thread.sleep() method can take t1 as an argument.
(B) The Object.notify() method can take t1 as an argument.
(C) The Thread.yield() method can take t1 as an argument.
(D) The Thread.setPriority() method can take t1 as an argument.
(E) The Object.notify() method arbitrarily chooses which thread to notify.
What is the result?
(A) Compilation fails.
(B) An exception is thrown at runtime.
(C) The code executes normally and prints "bar".
(D) The code executes normally, but nothing prints.
From another thread, what provides the most reliable way to ensure that foo will stop executing wait()?
(A) foo.notify();
(B) bar.notify();
(C) foo.notifyAll();
(D) Thread.notify();
(E) bar.notifyAll();
Which two statements are true? (Choose two.)
(A) The output could be 8-1 7-2 8-2 7-1
(B) The output could be 7-1 7-2 8-1 6-1
(C) The output could be 8-1 7-1 7-2 8-2
(D) The output could be 8-1 8-2 7-1 7-2
What is the result?
(A) The code will deadlock.
(B) The code may run with no output.
(C) An exception is thrown at runtime.
(D) The code may run with output "0 6".
(E) The code may run with output "2 0 6 4".
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.
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".
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
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();
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.
(AB) Wrapping the statements within doThings() in a synchronized(new Object()){} block would make the
class thread-safe.
Place a result onto each method call to indicate what would happen if the method call were inserted at line 9.
Note: Results can be used more than once.
Place the code into position to create a class that maps from Strings to integer values. The result of execution
must be [one]. Some options may be used more than once.
【非選題】 218
Place the code elements in position so that the Flags2 class will compile and make appropriate use of the
wait/notify mechanism. Note You may reuse code elements.
【非選題】 237
Place the code elements into the class so that the code compiles and prints "Run. Run. doIt. " in exactly that
order. Note that there may be more than one correct solution.
寫作批改
VIP與詳解卡管理
