COSC 1337 Test 2 Review
Which of the following is not a java.io package output class: All of these are java.io output classes FileWriter OutputStream PrintWriter Writer
All of these are java.io output classes
Which of the following is not a method of exception classes: All of these are valid answers toString() getMessage() printStackTrace()
All of these are valid answers
When a class implements an interface, we inherit any default, public, and static methods but we must provide method bodies for all the abstract methods.
true
When we open a file for appending, we will be adding data to the end of the file.
true
How do you instantiate an object from an abstract class?
you cannot
You need to read objects from a text file. What input class would be the most appropriate? FileInputStream InputStream Scanner ObjectInputStream
ObjectInputStream
Which of the following output classses is an abstract superclass?
OutputStream
Given the code snippet below, what is the output of this code sequence: // b2 is a B object reference System.out.println(b2.foo3());
A version of foo3() is called Hi
Which of the following can be interface members: a. All of these b. Constants c. Methods d. Other interfaces e. Classes
All of these
Which of the following must be true in order to use polymorphism: a. The classes must all be in the same hierarchy b. All the subclasses override the same method c. A subclass object reference is assigned to a superclass object reference d. All of these e. The superclass object reference is used to call the overridden method
All of these
Given the code snippet below, what is the output of this code sequence: // b1 is a B object reference and number has been set to 10 System.out.println(b1.foo1);
B version of foo1() is called
An abstract class always serves as a subclass
False
Writer is a subclass of OutputStream.
False
Which of the following is not a Java.io input class: File FileInputStream InputStream Scanner ObjectInputStream
File? Scanner
Which of the following input classes is used to read raw bytes of data from a file? FileInputStream None of these Scanner ObjectInputStream
FileInputStream
Which of the following output classes is a convenience class specifically for writing characters to a file?
FileWriter
If the interface only has one abstract method to implement, what is the interface called?
Functional
Which of the following is an abstract superclass? ObjectInputStream FileInputStream InputStream Scanner
InputStream
In this code snippet, would a class extending Base be able to override the method fun? Why? abstract class Base {final void fun() { System.out.println("Derived fun() called"); }}
No, because fun() is a final method
Which of the following is true of polymorphism: a. Polymorphism allows the same method call to be used for any object in the hierarchy b. The fact that an object of a subclass is also an object of any of its superclasses is a basis for polymorphism c.Polymorphism allows us to perform a single action (method) in different ways d. all of the above
all of the above
To inherit from an interface, a class declares that it _________the interface.
implements
What Java keyword is used ina class header when a class is defined as inheriting from an interface?
implements
in what package can the RuntimeException class be found?
java.lang
Which of the following Scanner and File class methods can throw an exception? (You may need to select more than one answer) nextFloat() hasNextInt() Constructor for Scanner close()
nextFloat() hasNextInt() Constructor for Scanner
When we associate a file with an input stream or output stream, we are ...
opening the file
The _____ exception class method will print the line number of the code that caused the exception.
printStackTrace()
You have been assigned to create a public interface called Library. Which of the following uses the correct syntax for defining it?
public interface Library { // body of interface }
If a class contains an abstract method, then
the class must be declared as abstract
If a class contains an abstract method, then ...
the class must be declared as abstract
When we open a file for writing,
the contents of the file are deleted, if any,
abstract class Base { void fun() { System.out.println("Base fun() called"); } } class Derived extends Base { } class Main {public static void main(String args[]) {Derived d = new Derived(); d.fun(); }}
this code will run without any problem
A Java class can implement one or more interfaces.
true
A class can implement 0, 1, or more interfaces
true
A variable defined within a try block is not local to just that block.
true
All interfaces are abstract
true
An abstract method is a method that is declared without an implementation
true
Calling the close method on a file is optional.
true
If a subclass does not provide implementations for all of the abstract methods in its parent class, then it must also be declared as abstract
true
If the code in the try block could generate multiple exception types, we can provide multiple catch blocks to handle the exceptions.
true
In Java, the abstract modifier must be applied to each abstract method.
true
In Java, we use the modifier abstract on the class header to declare a class as abstract.
true
System.in and System.err should not be closed.
true
The Exception class is the superclass of all exception classes.
true
The java.io package contains classes for input and output operations.
true
The scanner class can be used to read from a text file.
true
Given the code snippet below, what is the error? public class K {public void mys();}
Class K and method mys must be declared abstract
You are writing a program that will read in integer data from a text file. Which of the following exceptions should be accounted for if you use try-with-resources? (You may need to select more than one answer)
NoSuchElement Exception FileNotFound Exception
The extends keyword applies to ...
a class inheriting from another class
Which of the following best describes an abstract class in Java:
a class that is declared abstract
Which of the following statements is most accurate:
The first catch block with a parameter that matches the exception thrown will execute, then any remaining catch blocks will be skipped
Using the code snippet below, identify the error in this code sequence: C c2;c2 = new D(); There is no constructor for C or D There is no error Because C is an abstract class, it cannot be instantiated
There is no error
Which of the following is NOT TRUE about abstract classes in Java:
They can be instantiated
Multiple classes can inherit from an abstract class
True
RuntimeException is a superclass of InputMismatchException.
True
Unchecked exceptions are always subclasses of Error or RuntimeException.
true
Which of the following is not a valid type of method in an interface: All of these are valid public abstract public default private
alll of these are valid
If we open a file for reading and the file does not exist ...
an exception is thrown
In Java, multiple inheritance is implemented using the concept of
an interface
Illegal operations generate ______.
exceptions
An abstract class cannot be declared but it can be instantiated
false
At compile-time, the JVM will determine to which class in the hierarchy the object belongs and calls the appropriate version of the method for that class.
false
Code that could generate a checked exception does not have to be coded within a try block.
false
IOException is an example of an unchecked exception.
false
In Java, if a class contains abstract methods it does not have to be declared abstract
false
In polymorphism, not all the subclasses have to override the same method
false
Interfaces can be instantiated
false
NumberFormatException must be coded within a try block because it is an unchecked exception.
false
The IndexOutOfBounds exception class is a subclass of IOException.
false
The curly braces around the various try, catch, and finally blocks are required only if the block contains more than one statement.
false
This method is abstract: public void myMethod( ) { }
false
Try/catch blocks are useful because they can replace selection statements, which results in CPU time savings.
false
When coding a try and catch block, it is mandatory to code a finally block.
false
in Java, an abstract class is a template definition of methods and variables of a class that include one or more abstract methods
false
Scanner is in the java.io package.
false, it is in java.util
A ________ block contains code to execute regardless of whether an exception occurs.
finally
Which method only returns a message indicating the cause of the exception:
getMessage()
_________ refers to an attempt to recover from an exception and continue running the program.
handling the exception