Set - 5

Question 1 :

What is a native method?

Answer :

A native method is a method that is implemented in a language other than Java.


Question 2 :

Can a for statement loop indefinitely?

Answer :

Yes, a for statement can loop indefinitely. For example, consider the following: for(;;) ;


Question 3 :

What are order of precedence and associativity, and how are they used?

Answer :

Order of precedence determines the order in which operators are evaluated in expressions. Associatity determines whether an expression is evaluated left-to-right or right-to-left


Question 4 :

When a thread blocks on I/O, what state does it enter?

Answer :

A thread enters the waiting state when it blocks on I/O.


Question 5 :

To what value is a variable of the String type automatically initialized?

Answer :

The default value of a String type is null.


Question 6 :

What is the catch or declare rule for method declarations?

Answer :

If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.


Question 7 :

What is the difference between a MenuItem and a CheckboxMenuItem?

Answer :

The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.


Question 8 :

What is a task's priority and how is it used in scheduling?

Answer :

A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks.


Question 9 :

What class is the top of the AWT event hierarchy?

Answer :

The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.


Question 10 :

When a thread is created and started, what is its initial state?

Answer :

A thread is in the ready state after it has been created and started.


Question 11 :

Can an anonymous class be declared as implementing an interface and extending a class?

Answer :

An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.


Question 12 :

What is the range of the short type?

Answer :

The range of the short type is -(2^15) to 2^15 - 1.


Question 13 :

What is the range of the char type?

Answer :

The range of the char type is 0 to 2^16 - 1.


Question 14 :

In which package are most of the AWT events that support the event-delegation model defined?

Answer :

Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.


Question 15 :

What is the immediate super class of Menu?

Answer :

MenuItem


Question 16 :

What is the purpose of finalization?

Answer :

The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.


Question 17 :

Which class is the immediate super class of the MenuComponent class.

Answer :

Object


Question 18 :

What invokes a thread's run() method?

Answer :

After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.


Question 19 :

What is the difference between the Boolean & operator and the && operator?

Answer :

If an expression involving the Boolean & operator is evaluated, both operands are evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated. If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.


Question 20 :

Name three subclasses of the Component class.

Answer :

Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent


Question 21 :

What is the GregorianCalendar class?

Answer :

The GregorianCalendar provides support for traditional Western calendars.


Question 22 :

Which Container method is used to cause a container to be laid out and redisplayed?

Answer :

validate()


Question 23 :

What is the purpose of the Runtime class?

Answer :

The purpose of the Runtime class is to provide access to the Java runtime system.


Question 24 :

How many times may an object's finalize() method be invoked by the garbage collector?

Answer :

An object's finalize() method may only be invoked once by the garbage collector.


Question 25 :

What is the purpose of the finally clause of a try-catch-finally statement? garbage collector?

Answer :

The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.


Question 26 :

What is the argument type of a program's main() method?

Answer :

A program's main() method takes an argument of the String[] type.


Question 27 :

Which Java operator is right associative?

Answer :

The = operator is right associative.


Question 28 :

What is the Locale class?

Answer :

The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.


Question 29 :

Can a double value be cast to a byte?

Answer :

Yes, a double value can be cast to a byte.


Question 30 :

What is the difference between a break statement and a continue statement?

Answer :

A break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.


Question 31 :

What must a class do to implement an interface?

Answer :

It must provide all of the methods in the interface and identify the interface in its implements clause.


Question 32 :

What method is invoked to cause an object to begin executing as a separate thread?

Answer :

The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.


Question 33 :

Name two subclasses of the TextComponent class.

Answer :

TextField and TextArea


Question 34 :

What is the advantage of the event-delegation model over the earlier event-inheritance model?

Answer :

The event-delegation model has two advantages over the event-inheritance model. First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component's design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model.


Question 35 :

Which containers may have a MenuBar?

Answer :

Frame


Question 36 :

How are commas used in the initialization and iteration parts of a for statement?

Answer :

Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.


Question 37 :

What is the purpose of the wait(), notify(), and notifyAll() methods?

Answer :

The wait(),notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods.


Question 38 :

What is an abstract method?

Answer :

An abstract method is a method whose implementation is deferred to a subclass.


Question 39 :

How are Java source code files named?

Answer :

A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.


Question 40 :

What is the relationship between the Canvas class and the Graphics class?

Answer :

A Canvas object provides access to a Graphics object via its paint() method.


Question 41 :

What are the high-level thread states?

Answer :

The high-level thread states are ready, running, waiting, and dead.


Question 42 :

What value does read() return when it has reached the end of a file?

Answer :

The read() method returns -1 when it has reached the end of a file.


Question 43 :

Can a Byte object be cast to a double value?

Answer :

No, an object cannot be cast to a primitive value.


Question 44 :

What is the difference between a static and a non-static inner class?

Answer :

A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.


Question 45 :

What is the difference between the String and StringBuffer classes?

Answer :

String objects are constants. StringBuffer objects are not.


Question 46 :

If a variable is declared as private, where may the variable be accessed?

Answer :

A private variable may only be accessed within the class in which it is declared.


Question 47 :

What is an object's lock and which objects have locks?

Answer :

An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.


Question 48 :

What is the Dictionary class?

Answer :

The Dictionary class provides the capability to store key-value pairs.


Question 49 :

How are the elements of a BorderLayout organized?

Answer :

The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.


Question 50 :

What is the % operator?

Answer :

It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.


Question 51 :

When can an object reference be cast to an interface reference?

Answer :

An object reference be cast to an interface reference when the object implements the referenced interface.


Question 52 :

What is the difference between a Window and a Frame?

Answer :

The Frame class extends Window to define a main application window that can have a menu bar.


Question 53 :

Which class is extended by all other classes?

Answer :

The Object class is extended by all other classes.


Question 54 :

Can an object be garbage collected while it is still reachable?

Answer :

A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..


Question 55 :

Is the ternary operator written 

x : y ? z or x ? y : z ?

Answer :

It is written 

x ? y : z


Question 56 :

What is the difference between the Font and FontMetrics classes?

Answer :

The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.


Question 57 :

How is rounding performed under integer division?

Answer :

The fractional part of the result is truncated. This is known as rounding toward zero.


Question 58 :

What happens when a thread cannot acquire a lock on an object?

Answer :

If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.


Question 59 :

What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

Answer :

The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.


Question 60 :

What classes of exceptions may be caught by a catch clause?

Answer :

A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.


Question 61 :

If a class is declared without any access modifiers, where may the class be accessed?

Answer :

A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.


Question 62 :

What is the SimpleTimeZone class?

Answer :

The SimpleTimeZone class provides support for a Gregorian calendar.


Question 63 :

What is the Map interface?

Answer :

The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.


Question 64 :

Does a class inherit the constructors of its superclass?

Answer :

A class does not inherit constructors from any of its super classes.


Question 65 :

For which statements does it make sense to use a label?

Answer :

The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.


Question 66 :

What is the purpose of the System class?

Answer :

The purpose of the System class is to provide access to system resources.


Question 67 :

Which TextComponent method is used to set a TextComponent to the read-only state?

Answer :

setEditable()


Question 68 :

How are the elements of a CardLayout organized?

Answer :

The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.


Question 69 :

Is &&= a

valid Java operator?

Answer :

No, it is not.


Question 70 :

Name the eight primitive Java types.

Answer :

The eight primitive types are byte, char, short, int, long, float, double, and boolean.