Cs520 Quiz Reviews

Given the following declarations:

int a = 10;
int b = 20;

the expression.(++b - a++) will evaluate to

Consider the following segment of code:

int length = 10; int sum = 0;

// insert a definition of idx here

while (idx <= length)

{

sum += idx;

idx++;

}

What is the minimum value of idx to be used before the loop so the sum would not change inside the loop?

Which of the following loop statements always have their body executed at least once?
-The while loop
-Correct The do-while loop
-The for loop
-None of the choices

Given:

Which of the following, inserted at line 4, will prevent line 6 (y++;) from executing?

-int y = x;
-int y = 10;
-int y = 11;
-None of the given options

Within the following code:

int balance = 11;

while(balance-- >= 1)

{

if(balance > 9)

continue;

balance -= 9;

}

How many times is "continue" executed?

Which of the following is the correct sequence of declaring the main() method of a Java application?

public static void main(String[] args)
public void static main(String[] args)
static public void main(String[] args)
public void static main()

Given the following declarations:

int age = 30;
double salary = 25000 ;

which one of the following is a valid assignment statement?

age = salary / 100;
salary = 100 * age;
age = salary - 10000;
age = salary * age;

The System.out.println("hello") method:

Given the following declarations:

int a = 10;
int b = 30;
int c = 20;

the expression.(a + b / c + a) will evaluate to

Which of the following is not a keyword of Java?
class
public
keyword
void

Which one of the following lines is not a properly formatted comment?
a. /*
this is a comment
*/
b. // This is a comment
c. /* This is a comment */
d. //
this is a comment
//

What is the relationship between .java and .class files?

In Java, a statement block is delimited by:

Java compiles the source code into an intermediate language called byte-code. What is byte-code?

Which one of the following is a correct assignment statement for the variable x?
int x = 20,
double x = 20;
int 20 = x;
double 20.0 = x;

Which one of the following is true about Java?

a. It is not case sensitive.

b. It can be compiled using the C++ compiler.

c. It is one type of 4th generation language such as SQL.

d. It is object oriented and is widely used in web applications.

A variable whose meaning is confined to an object of a class is called

When you want the parameters in a method to be the same as the instance variables, you use the _____ keyword.

The modifier private means that an instance variable can be accessed by name outside of the class definition

Analyze the following code:

class Test {

public static void main(String[] args) {
System.out.println(xMethod((double)5));

}

public static int xMethod(int n) {

System.out.println("int");

return n;

}

public static long xMethod(long n) {

System.out.println("long");

return n;

}

}

What is the output of this code?

Which of the following statements is true about the static modifier?

-A static variable cannot change its value.

-A static method is often written in a non-Java language and exists outside of JVM.

-A static method can access instance variables

-A static variable is shared by all the instances of the class

Which of the following does not overload the method

-public int myMethod(int i, double a) { }

-public double myMethod(double b, int j){ }

-public int myMethod(double a, double b, int i){ }

-public int myMethod(int a, int i) { }

Consider the following code:

class Test

{

Test(){...}

Test(int x){...}

void method(){...}

}

Which of the following code fragments, using the class defined above, would generate a compile error? The ellipses {...} are used here to indicate the presence of some code.

What is the difference between static variable and instance variable?

Which of the following statements are correct about constructor? Three choices are applicable.

- Constructor can ONLY be called when a new instance of the class has to be created.

- Constructor can have multiple overloaded versions.

-If you do not declare a constructor, then the class has no constructor; therefore can not be instantiated.

- It always has the same name as the name of the class.

A class can be defined by extending another class. It is called _______________ .

The Object class and the Integer class both have toString() methods. Note that the Object class is the root class of Java hierarchy.

What output is generated when Test is run?

A method that performs some actions but does not return a value can be declared a __________ method.

Which of the following is NOT correct about declaring a class?

-The body of the class is bracketed by {}

-The name of the class must be after the "class" keyword

-It can contain instance variables and instance methods

-It must be declared with at least one instance variable

A variable whose meaning is confined to a method definition is called an/a

Tokenizing the string "a;b;c;d" using the default delimiter results in

Consider the following code fragment:

public class ExceptionHandlingNote{

public static void main(String[] args){

String x;

System.out.println(x);

}

}

Which of the following is true:

It prints out 0

It prints out null

It prints out nothing

None of the choices is true

Which of the following are the CORRECT ways of declaring a string?

String s = new String("Hello");

String s = 'hello';

char[] s = "Hello";

String s = 123;

If an object must be written to and read back from a file in its entirety, the class definition of that object must

Consider the following line of code:
String str = new String("Hello");
Which of the following lines of code modify the string to which str refers?

-str.substring(2);

-str.replace('H', 'M');

-str.trim();

-None of the choices.

The StringTokenizer class is used for

Which of the following statement is correct about Exception?

-Exception is not a class.

-An exception must be caught before being thrown.

-An exception can be either handled or be declared as thrown.

-try{} block must always be used to capture an exception.

Which one of the following classes from the java.io package can be used for writing objects to a file?

-ObjectOutputStream

-BufferedReader

-FileReader

-File

Which of the following is correct about the String class?

-The replace() method will modify the string object which is calling the method.

-The trim() method will remove the white space at the end of the current string object.

-substring() method will return a new string object, instead of modifying the current string object.

-String class is equivalent to string class.

You can not place a try block and its following catch blocks inside a larger try block or inside a larger catch block.

The catch clause has ________ parameter(s).

Ye code

new StringBuffer("abcd").reverse().substring(1, 2)

results in the following string:

The method trim() of the String class trims off:

Tokenizing the string "a,b;c,d;e,f" using the comma delimiter results in

Suppose

String s= "Java";

which of the following will change s to "java". More than one choice is valid.

-s.toLowerCase();

-s.toUpperCase();

-s=s.toLowerCase();

-s=s.replace('J','j');

Which one of the following classes from the java.io package can be used for writing text data to a file?

-PrintWriter

-BufferedReader

-FileReader

-File

Suppose s1 and s2 are two non-empty strings with the length of s1 greater than the length of s2. Which of the following statements or expressions will generate a compile error?

-String s3 = s1 + s2;

-char c = s1.substring(0,1);

-s2 = s1.replace('s', 's');

-s1 = s2.substring(s1.length());

What is true about the following partial code?

if("String".toString() == "String")

System.out.println("Equal");

else

System.out.println("Not Equal");

Tokenizing the string "a,b;c,d;e,f" using the semi-colon delimiter results in

Which of the following statements is true about exception handling?

-Exception is not a type of class

-When you have a try{} clause, you must use catch as well

-Some exceptions do not require the programmer to handle using try-catch

-When a program would possibly throw an exception, this exception must be caught using a try clause

A ___________ is the unit of space on the screen that Java uses for graphics.

Consider the code

button.addActionListener(this);

which of the following is NOT correct?

-The "this" referred to in the code must be an implementation of one or more listeners.

-The code will register the button with a listener.

-The listener that "this" referrs to should have the method actionPerformed(ActionEvent e) implemented.

-One must declare the button to implement one or more Listeners.

The ____________________ is an object that waits for an event to occur and responds in some way when it does.

Which of the following draws a circle whose center position is (400, 400) and whose radius is 50?
-g.drawCircle(350, 350, 100, 100);
-g.drawOval(350, 350, 100, 100);
-g.drawCircle(400, 400, 50, 50);
-g.drawOval(400, 400, 50, 50);

A button control should have a registered ___________ associated with it to take some action when the user clicks on it.

In event-driven programming, a Java program includes one or several of the following steps:

1. create a component object and add it to a container

2. specify which class implements a component's event listener

3. implement an event handler method and specify what program method calls it

4. register the component as a listener for the application frame

Which steps actually have to be included?

Given the sequence of the following statements,

g.drawLine(50,100,150,100);

g.drawLine(50,50,150,50);

g.drawLine(150,50,150,100);

g.drawLine(50,50,50,100);

which of the following can replace the above sequence?

-g.drawRect(150,50,100,50);

-g.drawRect(50,100,100,50);

-g.drawRect(50,50,100,50);

-g.drawRect(100,100,50,50);

Suppose an ArrayList of String objects, myList, has the strings "1", "2", and "3" added to it in that order.

The code

ListIterator it = myList.listIterator();

while (it.hasNext()) {

System.out.print(it.next());

it.previous();

}

results in the following output:

Suppose a HashSet of String objects, mySet, has the strings "1", "2", "3", "4", and "5" added to it in that order. When iterating over the elements in this set, the output

Suppose a HashSet of String objects, mySet, has the strings "1", "2", "3", "4", and "5" added to it in that order. The same set of strings is added one more time. The size of the mySet will be

Suppose we have an array of String objects (with at least one element) identified by the variable 'names'. Which of the following loops will CORRECTLY process each element in the array?

-for (int i = 0; i < names.length; i++) ...

-for (int i = 0; i < names.length(); i++) ...

-int i = 0; while (i <= names.length) {.... i++; }

-None of the above

Assume the signature of the method xMethod is as follows:

public static void xMethod(double[] a)

Which of the following could be used to invoke xMethod(double[] a)?

-xMethod(5);

-xMethod({3, 4});

-xMethod(new int[2]);

-xMethod(new double[2]);

Consider the following array declaration inside the body of a method.

int[ ] values = new int[10];

Accessing the array element, values[0], right after the above declaration results in:

Which of the following initializer correctly initializes the elements of an array named myDoubles?

-double myDoubles[double] = {0.0, 1.0, 1.5, 2.0, 2.5};
-double myDoubles[5] = new double (0.0, 1.0, 1.5, 2.0, 2.5);
-double [ ] myDoubles = {0.0, 1.0, 1.5, 2.0, 2.5};
-array myDoubles[double] = {0.0, 1.0, 1.5, 2.0, 2.5};

Consider the following array declaration inside the body of a method.

String[ ] values = new String[10];

Invoking the length method on the array element, values[0], right after the above declaration results in:

Consider the following array declaration inside the body of a method.

int[ ][ ] values = {{1},{2,3},{4,5,6}};

The length of the values array is:

Consider the following array declaration inside the body of a method.

int[ ][ ] values = {{1},{2,3},{4,5,6}};

The expression

(values[0] + values[1])

results in:

Consider the following array declaration inside the body of a method.

int[ ][ ] values = {{1},{2,3},{4,5,6}};

The expression.(values[1][1] + values[2][2]) results in:

Consider the following ArrayList declaration inside the body of a method.

ArrayList myList = new ArrayList();

Accessing the element, myList.get(0), right after the above declaration results in:

Consider the following ArrayList declaration inside the body of a method.

ArrayList myList = new ArrayList();

Which of the following statements are true before the above ArrayList is modified? More than one choice may be applicable.

Consider the following ArrayList declaration and its iterator inside the body of a method.

ArrayList myList = new ArrayList();

Iterator it = myList.iterator();

Invoking the it.next() method right after the above declaration results in:

Suppose an ArrayList of String objects, myList, has the strings "1", "2", and "3" added to it in that order.

The code

Iterator it = myList.iterator();

while (it.hasNext())

System.out.print(it.next());

results in the following output:

Assume that a LinkedList is used for a queue implementation and has the strings "1", "2", "3", "4", and "5" added to it in that order. The peek method results in the string

Assume that a LinkedList is used for a queue implementation and has the strings "1", "2", "3", "4", and "5" added to it in that order. After invoking theremove, the peek method results in the string

Given an empty ArrayDeque of String objects, myDeck, the strings "1", "2", "3", and "4" are added to it using the addFirst and addLast methods alternatively as shown below.

myDeck.addFirst("1");
myDeck.addLast("2");
myDeck.addFirst("3");
myDeck.addLast("4");

The expression myDeck.removeFirst() + myDeck.removeLast() results in

Given an empty ArrayDeque of String objects, myDeck, the strings "1", "2", "3", and "4" are added to it using the addFirst and addLast methods alternatively as shown below.

myDeck.addFirst("1");
myDeck.addLast("2");
myDeck.addFirst("3");
myDeck.addLast("4");

After invoking the removeFirst and removeLast methods, the peek method results in

Given an empty LinkedList of Integer objects, myList, the values 1, 2, 3, 4, and 5 are added to it using the addFirst method.

myList.addFirst(1);
myList.addFirst(2);
myList.addFirst(3);
myList.addFirst(4);
myList.addFirst(5);

The expression myList.get(1) + myList.get(2) results in

Given an empty LinkedList of Integer objects, myList, the values 1, 2, 3, 4, and 5 are added to it using the addLast method.

myList.addLast(1);
myList.addLast(2);
myList.addLast(3);
myList.addLast(4);
myList.addLast(5);

The expression myList.get(1) + myList.get(2) results in

Given an empty LinkedList of Integer objects, myList, the values 1, 2, 3, 4, and 5 are added to it using the addLast method.

myList.addLast(1);
myList.addLast(2);
myList.addLast(3);
myList.addLast(4);
myList.addLast(5);

The expression myList.contains("2") returns true.

Suppose a Stack of String objects, myStack, has the strings "1", "2", "3", "4", and "5" pushed onto it in that order. The myStack.pop() method results in the string

Suppose a Stack of String objects, myStack, has the strings "1", "2", "3", "4", and "5" pushed onto it in that order. After invoking the peek() method, the pop()method results in the string

Suppose a Stack of String objects, myStack, has the strings "1", "2", "3", "4", and "5" pushed onto it in that order. After invoking the pop() method, the peek()method results in the string

Consider the following class definition.

public class Employee {

private int salary = 50000;

public void payRaise() {

salary += 500;

}

public void payCut() {

salary -= 500;

}

}

Suppose that there are two threads (the Supervisor thread and the CEO thread) with access to the same Employee object. One thread attempts to give thepayRaise while the other thread attempts a payCut concurrently. What would be the result?

Consider the following class definition.

public class TestThread implements Runnable{

public void run() {

System.out.println("Hello");

}

}

The code invoking the start() method on a Thread object created using the TestThread object

new Thread(new TestThread()).start();

Which one of the following statements causes the current thread to sleep for a random amount of time up to a maximum of one minute.
-Thread.sleep(60000 * Math.random());
-Thread.sleep((long) (60000 * Math.random()));
-Thread. .sleep((long) (10000 * Math.random()));
-Thread.sleep(10000 * Math.random());

Consider the following class definition.

public class Employee {

private int salary = 50000;

public synchronized void payRaise() {

salary += 500;

}

public synchronized void payCut() {

salary -= 500;

}

}

Suppose that there are two threads (the Supervisor thread and the CEO thread) with access to the same Employee object. One thread attempts to give thepayRaise while the other thread attempts a payCut concurrently. What would be the result?

Consider the following class definition.

public class TestThread {

public void run() {

System.out.println("Hello");

}

}

The code invoking the start() method on a Thread object created using the TestThread object

new Thread(new TestThread()).start();

results in:

Consider the following class definition.

class Test {

public synchronized void foo()
throws InterruptedException {

wait();

System.out.println("Goodbye");

}

public synchronized void bar()
throws InterruptedException {

wait();

System.out.println("Hello");

}

}

Suppose two threads running concurrently share the same Test object. One thread invokes the bar method and the other thread invokes the foo method of the same object. What would be the result?

Consider the following class definition.

public class TestThread {

public void run() {

System.out.println("Hello");

}

}

The code invoking the start() method on a TestThread object results in:

Consider the following class definition.

public class TestThread extends Thread{
public void start() {

System.out.println("Goodbye");

}

public void run() {

System.out.println("Hello");

}

}

The code invoking the start() method on a TestThread object results in:

Consider the following class definition.

class Test {

public synchronized void foo() {

bar();

System.out.println("Goodbye");

}

public synchronized void bar() {

System.out.println("Hello");

}

}

When a thread invokes the foo() method on a Test object, (when no other thread is sharing this object), what would be the result?

Consider the following class definition.

class Test {

public synchronized void foo() throws InterruptedException {

wait();

System.out.println("Goodbye");

}

public synchronized void bar() {

System.out.println("Hello");

notify();

}

}

Suppose two threads share the same Test object. One thread always invokes the bar method first before the other thread invokes the foo method of the same object. What would be the result?