A.Direction d = NORTH；
B.Nav.Direction d = NORTH；
C.Direction d = Direction.NORTH；
D.Nav.Direction d = Nav.Direction.NORTH；

A.hi hi
B.hi world
C.world world
D.Compilation fails.
E.An exception is thrown at runtime.

A.public class Circle implements Shape {private int radius；}
B.public abstract class Circle extends Shape {private int radius；}
C.public class Circle extends Shape {private int radius；public void draw（）；}
D.public abstract class Circle implements Shape { private int radius；public void draw（）；}
E.public class Circle extends Shape {private int radius；public void draw（） {/* code here*/}}

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.

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

A.4
B.5
C.8
D.9

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.

A.It is possible for more than two threads to deadlock at once.
B.The JVM implementation guarantees that multiple threads cannot enter into a deadlocked state.
C.Deadlocked threads release once their sleep（） method’s sleep duration has expired.
D.Deadlocking can occur only when the wait（）， notify（）， and notifyAll（） methods are used incorrectly.
E.It is possible for a single-threaded application to deadlock if synchronized blocks are used incorrectly.
F.If a piece of code is capable of deadlocking， you cannot eliminate the possibility ofdeadlocking by insertinginvocations of Thread.yield（）.

A.java.lang.RuntimeException： Problem
B.run.java.lang.RuntimeException： Problem
C.End of method.java.lang.RuntimeException： Problem
D.End of method.run.java.lang.RuntimeException： Problem
E.run.java.lang.RuntimeException： ProblemEnd of method