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Arraylist Test

Last updated almost 2 years ago

13 questions

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Question 1

1.

Which of the following code segments could fill /* blank / so the code would add the first and third element of list? ArrayList<Object> list = new ArrayList<Object>(); list.add(5); list.add("abc"); list.add(4); list.add(1.2); list.add('a'); list.add("10"); int i = / blank */

a. list.get(0) + list.get(2);

b. list.get(1) + list.get(3);

c. (int)(list.get(0)) + (int)(list.get(2));

d. (int)list.get(0) + (int)list.get(2);

e. more than one of these

Question 2

2.

What is output by the code below? String[] ray; ray = new String[4]; ray[1] = "one"; ray[2] = "two"; ray[3] = "three"; ray[0] = ray[2]; ray[2] = null; System.out.println( ray[0] );

a. one

b. two

c. three

d. null

e. 0

Question 3

3.

Which of the descriptions provided below describes the best way to improve the code shown below to ensure that all of the occurrences of string one will be removed?
public static void removeAllOnes(ArrayList<String> all)
{
int spot = all.size() - 1;
while ( spot > 0 )
{
if( all.get(spot).equals("one") )
all.remove(spot);
spot--;
}
}

a. Change the while loop to a for loop.

b. Change the while loop to an if statement.

c. Add an else before spot-- in the loop.

d. Change the while loop condition to ( spot >= 0 )

e. Change spot-- to spot++.

Question 4

4.

What is output by the code below? List<String> bigList = new ArrayList<String>(); bigList.add(0,"one"); bigList.add("two"); bigList.add(0,"three"); bigList.add("four"); bigList.add(0,"five"); bigList.set(2,"six"); bigList.set(3,"seven"); out.println( bigList.indexOf("three") );

a. 2

b. 1

c. 0

d. 4

e. 5

Question 5

5.

Consider the following class definitions.
public class Cat
{
private String name;
private int age;

public String getName()
//implementation not shown
public int getAge()
//implementation not shown
//constructors and other methods not shown
}

public class CatBarn
{
private Cat[] kitties; //assume kitties has stuff in it

//returns the number of kittes older than > age
public int countCats( int age ){
/* blank /
}
//constructors and other methods not shown
}

Which of the following code segments shown below could be used to replace
/ blank */ so that method countCats() will work as intended?
I.
int cnt = 0;
for( Cat c : kitties )
if( c > age )
cnt = cnt + 1;
return cnt;

II.
int cnt = 0;
for( Cat c : kitties )
if( c.getAge() > age )
cnt = cnt + 1;
return cnt;

III.
int cnt = 0;
for( int i = 0; i < kitties.length; i++ )
if( kitties[i].getAge() > age )
cnt += 1;
return cnt;

I and II only

II only

II and III only

I only

III only

Question 6

6.

Which of the following code segments could fill /* blank / so the code would retrieve the numeric value of the last element?

ArrayList<Object> list = new ArrayList<Object>();
list.add(5);
list.add("abc");
list.add(4);
list.add(1.2);
list.add('a');
list.add("10");

int i = / blank */ ;

Integer.parseInt((String)(list.get(list.size()-1)))

Integer.parseInt(list.get(list.size()-1))

more than one of these

(int)(list.get(list.size()-1))

list.get(list.size()-1)

Question 7

7.

Method removeAllOnes should go through the entire ArrayList and remove all occurrences of the word one. Examine the code below and determine if the code works or if the code has issues. Select the best description of the code from the answer choices shown below.

public static void removeAllOnes(ArrayList<String> all)
{
for(int spot=0; spot < all.size(); spot++)
{
if( all.get(spot).equals("one") )
all.remove(spot);
}
}

The code will result in a runtime error.

The code will remove all occurrences of one.

The code will remove none of the occurrences of the word one.

The code will remove some of the occurrences of one, but not all of them.

The code will remove only the first occurrence of one.

Question 8

8.

Consider the following Pig class and client code below.
class Pig
{
public Pig( int x, String y )
{
//code not shown
}
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////
//client code
ArrayList< Pig > list;
list = new ArrayList< Pig >();
/* blank /

Which of the following could fill / blank */ to add a Pig to the list?

I. list.add( 5 );
II. list.add( 5, "piggy" );
III. list.add( new Pig( 5, "piggy" ) ) ;

III only

II only

I and II only

I only

I and III only

Question 9

9.

What is output by the code below?
String[] ray;
ray = new String[4];
System.out.println( ray[0] );

one

three

0

two

null

Question 10

10.

Which of the following code segments could fill /* blank / so the code would add the first and fourth element of list?

ArrayList<Object> list = new ArrayList<Object>();
list.add(5);
list.add("abc");
list.add(4);
list.add(1.2);
list.add('a');
list.add("10");

double i = / blank */

(int)list.get(0) + (double)list.get(3);

(double)(list.get(0) + list.get(3));

list.get(1) + list.get(4);

It is not possible to add the 1st and 4th elements of this list.

list.get(0) + list.get(3);

Question 11

11.

Part A. Write the Row method blockCount(), as started below. blockCount() will count up how many Blocks there are in the Row that have a width and height equal to the supplied parameters. In writing blockCount() you may call any of the public methods of class Block and any of the public or private methods of class Row. Assume that all of the listed methods work as specified.

// This method counts up the number of Blocks with a height and width that match the provided params

public int blockCount( int width, int height ) {

//Code goes here//

}

Question 12

12.

B. Write the Row method tallestBlock(), as started below. tallestBlock() will go through the entire ArrayList of Block and return a reference to the Block that is the tallest. The tallest Block would be the block with the greatest height. In writing tallestBlock() you may call any of the public methods of the Block and Row classes. Assume that all the listed methods work as specified.

// This method will return a reference to the Block with the greatest height
// myBlocks contains at least one Block

public Block tallestBlock(){

//Code goes here//

}

Question 13

13.

Part C. Write the Row method level(), as started below. level() will go through the entire ArrayList of Block and make sure that the entire row has the same height as the tallest Block in the Row. In writing level() you may call any of the public methods of class Block and any of the public or private methods of class Row. Assume that all the listed methods work as specified.

// This method would set all Block to the same height as the tallest Block

public void level() {

//Code goes here//

}