Card 0 of 20
Which of the following blocks of code will output an evenly-spaced 2D array (i.e. an evenly-spaced matrix)? For example, a simple evenly-spaced matrix is:
1 2 3
4 5 6
7 8 9
There are several critical points to look at in the code given as possible answers above.
First, you need to make sure that the main output is not a new line. Thus, the following is incorrect:
System.out.println(matrix\[i\]\[j\]);
This would create a new line for every single value!
Next, you need to make sure that a new line is output after every row of the matrix. This is the final output statement. Thus, it cannot be:
System.out.print(" ");
This would only output a character with no new line.
Finally, for everything except for the first element of each row, you will need to output sufficient padding before the given element element (so as to make the matrix to be evenly-spaced). We are not going to be too particular here about the problem of very big numbers—the values are given to us as is. Note that it is insufficient to use a mere space for this. You should use a tab character (defined as '\t'). A space will not guarantee enough spacing (no pun intended)!
The correct answer has the following logic:
if(j != 0) {
System.out.print("\t\t");
}
This means "when the column is not the first column" (i.e. j != 0), "then output tabs to space sufficiently."
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Consider the following code:
for(int i = 1; i <= 10; i++) {
for(int j = 0; j < (20 - i * 2) / 2; j++) {
System.out.print(" ");
}
for(int j = 0; j < i * 2; j++) {
System.out.print("*");
}
for(int j = 0; j < (20 - i * 2) / 2; j++) {
System.out.print(" ");
}
System.out.println();
}
Describe the output of the code above.
This code is best explained by analyzing it directly. Comments will be provided in bold below:
// The loop runs from 1 to 10
for(int i = 1; i <= 10; i++) {
// First, you run through 0 to some number
// That number is computed by taking the current value of i, doubling it,
// subtracting that from 20, then dividing by 2.
// So, consider the following values for i:
// 0: 20 - 0 = 20; Divided by 2: 10
// 1: 20 - 2 = 18; Divided by 2: 9
// 2: 20 - 2 = 16; Divided by 2: 8
// etc...
// Thus, you will output single spaces that number of times (10, 9, 8...)
for(int j = 0; j < (20 - i * 2) / 2; j++) {
System.out.print(" ");
}
// Next, you will output an asterix i * 2 number of times. Thus, your
// smallest value is 2 and your largest 20.
for(int j = 0; j < i * 2; j++) {
System.out.print("*");
}
// This is just a repeat of the same loop from above
for(int j = 0; j < (20 - i * 2) / 2; j++) {
System.out.print(" ");
}
// This bumps us down to the next line
System.out.println();
}
Thus, you have output that basically has even padding on the left and right, with an increasing number of asterix characters (2, 4, 6, etc). This is an upward-facing arrow, having a point of width 2 and a base of width 20.
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Consider the following code:
What is the output of the method call mystery("Green eggs and ham")
The method String.split() splits a String into an array of Strings separated according to the expression within the method argument. The expression String.split("") splits the String at every character. The "for" loop concatenates the elements of the String array together, separated by a comma.
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public static void main(String[] args) {
int[][] x = {{4,5,6,7},{91,15,14,13}};
int[][] y = {{-13,4,41,14},{14,5,13,3}};
int[][] z = doWork(x,y);
for(int i = 0; i < z.length; i++) {
for(int j = 0; j < z[0].length;j++) {
System.out.print(z[i][j] + " ");
}
System.out.println();
}
}
``
public static int[][] doWork(int[][] a, int[][] b) {
int[][] ret = new int[a.length][a[0].length];
for(int i = 0; i < a.length; i++) {
for(int j = 0; j < a[i].length; j++) {
ret[i][j] = a[i][j] + b[i][j];
}
}
return ret;
}
What is the console output for the code above?
The doWork
method implements a relatively standard type of 2D array iteration, one that goes through each element. The outer loop goes through the first dimension of the array. Then, the inner loop provides index for the second dimension. From this, you get the total 2D index [i][j]
. The line ret[i][j] = a[i][j] + b[i][j];
actually performs the operation at the given index. Here, it performs an addition, combining the values at [i][j]
found in the two arrays. This gives you the sum at each index of ret
. The main method outputs each of these values, following the same standard algorithm for 2D array traversal.
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Given:
int\[\]\[\] myArray = { {1, 2},
{3, 4} };
What would the following statement print out to the console?
System.out.print(myArray\[1\]\[1\] + 10);
Before anything is printed out into the console, the following is first evaluated:
myArray\[1\]\[1\] + 10
myArray\[1\]\[1\] is referring to the item that is in row=1 and column=1 of myArray. Taking note that arrays start with row 0 and column 0, we see that the item in row 1 column 1 is the number 4. Now we have the following: 4+10. This evaluates to 14. Therefore, the Java print statement will print out the number 14 on the console.
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int a = 10, b = 5;
for(int i = 0; i < a; i+=2) {
for(int j = 0; j < i % b; j++) {
System.out.print("* ");
}
System.out.println();
}
What will be the console output for the code above?
All this problem requires is careful attention to the loop control variables. Notice that the first loop adds 2 to i every looping. This means that it will run for 0,2,4,6, and 8. Thus, a total of five lines will be printed.
Now, the second loop dictates the number of * characters that will be output per line. This is going to be based upon the result of the modulus i % b. Remember, modulus is a remainder calculation. Thus, you will have:
0 % 5 = 0
2 % 5 = 2
4 % 5 = 4
6 % 5 = 1
8 % 5 = 3
Hence, you will have the following (note the first line is empty, given the result of 0 % 5):
* *
* * * *
*
* * *
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class Base{
public:
void foo(int n) { cout << "Base::foo(int)
"; }
};
class Derive: public Base{
public:
void foo(double n) { cout << "Derived::foo(double)
";}
};
int main(){
Derived der;
der.foo(42);
}
The above code is written in C++, what is the output of the program?
This is an example of inheritance. The child class (Derived) is an inherited class of the parent class (Base). When the Derived object is created and the "foo" method is called, foo in the Derived class will be called. If there is the same method in the parent class and child class, the child's method will be called.
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What will the following code result in?
int main(){
int i = 7;
const int * ip = &i;
cout<< *ip << endl;
}
Let's take a look at the code.
int i = 7;
This line assigns 7 to the variable "i".
const int * ip = &i;
This line creates a constant int pointer and assigns the address of "i" to the pointer.
cout << *ip << endl;
This line prints the dereference of the pointer, which holds the value 7.
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What is the output of this program?
arr = \["hello", "my", "name", "is"\]
for (int i = 0; i < arr.length - 1; i++) {
System.out.println(arr\[i\]);
}
System.out.println("Sandra");
The words are printed on separate lines due to the System.out.println() call and then whatever is inside of the parentheses is printed on the next line. This call is different from System.out.print() which prints words on the same lines.
Therefore, the Sysytem.out.printIn gives("Sandra"):
hello
my
name
is
Sandra
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True or False.
The output of this code snippet will be "Hello, I'm hungry!"
public static void meHungry() {
String hungry = "hungry";
String iAm = "I'm";
String hello = "Hello";
String message = "";
if (hungry != null) {
message += hungry;
}
if (hello != null && iAm != null) {
message = hello + iAm + hungry;
}
System.out.println(message);
}
The message that is printed out is "Hello I'm hungry"
Notice there is no punctuation in the message. The code does not add punctuation to the message, but prints the words out in the same order as the phrase in the prompt. Be mindful of what's actually happening in the code.
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In Swift (iOS), give a description of what this method does.
func getDivisors(num: Int, divisor: Int) -> Bool {
var result: Bool = False
if (num % divisor == 0) {
result = True
}
println(result)
}
The modulus function "%" determines the remainder of a division. If I have 1 % 2, the remainder is 1. If I have 2 % 2, the remainder is 0. Therefore, if the remainder is equal to 0, then the number is divisible by the function. Thus, the method returns true if the number is evenly divisble by the divisor and false otherwise.
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Does the code compile and if yes, what is the the output?
public class Test
{
public static void main ( String \[\] args )
{
int x = 2;
if (x = 2)
System.out.println("Good job.");
else
System.out.println("Bad job);
}
}
It doesn't compile. It is supposed to be x == 2 within the if statement not x = 2. The if statement checks for booleans (only true or false) and cannot convert an integer into a boolean to meet that check.
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Which of the following code samples adequately uses constants?
Remember that a constant variable cannot be changed once it has been assigned. Normally, you assign the variable immediately on the same line as the declaration. However, if you were to create the constant and wait to assign a value, that would be find syntactically as well. Thus, the correct answer does not have a problem, though it might appear so at first if you did not know this. Now, remember that the way to declare a constant is to use the keyword "final". (The keyword "const" works in some other languages like C++.) All of the incorrect answers (other than the one using "const") alter the constant after it has been defined.
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In the following block of code, which of the following lines contains an error?
final int i = 20, j, k;
int l,m=50,n = 2;
j = n + m;
l = m * i + j;
for(int a = 0; a < m; a++) {
l += l;
}
m = 20 + j + n * i + m;
j = m + i;
k = 50 + 20 * j;
The line
j = m + i;
has an error because it contains a reassignment to a constant (final) variable. You are permitted to assign a constant on a line that is not the line of declaration. However, once you do this, you cannot reassign a value. The variable j was assigned a value on the line:
j = n + m;
Thus, the line above (j = m + i;) represents a re-assignment, hence causing an error.
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Class Person {
int height;
float weight;
``
public:
int getHeight();
void setHeight(int);
float getWeight();
void setWeight(float);
};
What is the access level of height
and weight
?
Until an access specifier is given, all class members are implicitly private. All members defined after an access specifier is used will will have that access level until another access specifier is explicitly invoked. Since no access specifier was used, weight
and height
are automatically private.
Note that virtual
is not an access keyword.
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Consider the following code:
public static class Clock {
private int seconds;
``
public Clock(int s) {
seconds = s;
}
``
public void setTime(int s) {
seconds = s;
}
``
public void setSeconds(int s) {
int hoursMinutes = seconds - seconds % 60;
seconds = hoursMinutes + s;
}
``
public void setMinutes(int min) {
int hours = seconds / 3600;
int currentSeconds = seconds % 60;
seconds = hours + min * 60 + currentSeconds;
}
}
Which of the following represents a method that returns the minute value of the clock?
This clock class is defined as having only seconds in its fields, so you have to convert this value for any of the accessors and mutators. Therefore, you need to perform careful (though simple) mathematics for this conversion. To calculate the number of minutes in a given number of seconds, you first need to remove the hours from total count. First, compute the hours using integer division (which will drop the fractional portion of the decimal). This is:
int hours = seconds / 3600;
Next, you need to figure out how many seconds are in that value of hours. This is helpful precisely because integer division drops the decimal portion. Thus, you will subtract off:
hours * 3600
from the total seconds.
This gives you the seconds that apply to the minutes and seconds of the time. Therefore, you will finally need to divide by 60 to isolate the minutes.
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Consider the following code :
public class Clock {
private int seconds;
``
public Clock(int s) {
seconds = s;
}
``
public void setTime(int s) {
seconds = s;
}
``
public void setSeconds(int s) {
int hoursMinutes = seconds - seconds % 60;
seconds = hoursMinutes + s;
}
``
public void setMinutes(int min) {
int hours = seconds / 3600;
int currentSeconds = seconds % 60;
seconds = hours + min * 60 + currentSeconds;
}
}
Which of the following defines a toString method that will output the time in 24-hour format in the following form:
1:51:03
(Notice that you need to pad the minutes and seconds. You can call 12 midnight "0".)
There are several points to be noted in this code. First, you need to calculate each of the constituent parts from the seconds stored in the class. The "display value" of seconds is relatively easy. This is just the remainder of a division by 60. Consider:
61 seconds => This is really 1 minute and 1 second.
155 seconds => This is really 2 minutes and 35 seconds.
So, you know that the display seconds are:
seconds % 60
You must compute the hours using integer division (which will drop the fractional portion of the decimal). This is:
int hours = seconds / 3600;
Next, you need to figure out how many seconds are in that value of hours. This is helpful precisely because integer division drops the decimal portion. Thus, you will subtract off:
hours * 3600
from the total seconds.
This gives you the seconds that apply to the minutes and seconds of the time. Therefore, you will finally need to divide by 60 to isolate the minutes.
Then, you must pad the values. This is not done using +=
, which would add the "0" character to the end of the string. Instead, it is done by the form:
secString = "0" + secString;
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Which of the following represents an acceptable definition of an interface?
An interface cannot have any member data or implementations for its methods. It only defines a set of methods that are required by anything that implements that interface. Therefore, the only option that is valid is the interface defined as Shape2D
.
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Which of the following represents a valid declaration of an interface and a class that implements that interface?
In order to implement an interface, you must use the syntax "implements implements Shape2D
. Also, you must make sure that all of your methods are defined in your class just as they are defined in the interface declaration. You will notice that a variety of the incorrect answers do not do this but instead have wrong types or names in various places.
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Consider the following code:
public static interface Shape2D {
public double getArea();
}
``
public static class Ellipse implements Shape2D {
private double r1,r2;
public Ellipse(double r1,double r2) {
this.r1 = r1;
this.r2 = r2;
}
public double getArea() {
return Math.PI * r1 * r2;
}
}
public static class Circle extends Ellipse {
private double radius;
public Circle(double r) {
super(r,r);
}
public double getArea() {
return super.getArea();
}
public double getCircumference() {
return Math.PI * 2 * radius;
}
}
``
public static void main(String[] args) {
Shape2D[] vals = {new Circle(5),new Ellipse(8,5)};
for(int i = 0; i < vals.length; i++) {
System.out.println("Area " + (i+1) + ": " + vals[i].getArea());
}
}
What is the output for this code?
We are dealing here both with the implementation of an interface as well as inheritance. Notice that the Circle
class has a getArea
method that uses the superclass's getArea
method. This equation is , but for the Circle
, so the equation is the same as the standard
. This loop will iterate through the objects, using the appropriate method in each case. Thus, you will get two values:
, which is relatively close to
or
.
, which is relatively close to
or
.
Those are close enough to help you estimate for the output.
(Notice that the line numbers need to be "1" and "2".)
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