Code Snippets-based MCQs

Soft Intro to Java with BlueJ (Objects & Classes)

Table of contents

Easy Level MCQs
Slightly harder MCQs

Easy Level MCQs

Given a Person class with a constructor that initializes the name and age of a person and a method getName that returns the name, what will be the output of the following code snippet?
```
Person p = new Person("Alice", 30);
System.out.println(p.getName());
```
Alice
30
null
Compilation error

Answer

Alice
Given a Rectangle class with a constructor that initializes its width and height, and a method area that returns the area of the rectangle, what will be the return value of the given method call?
```
Rectangle rect = new Rectangle(3, 4);
rect.area();
```
7
12
0
Compilation error

Answer

12
What will be the output of the following code snippet?
```
int a = 10;
int b = 20;
System.out.println(a + b + "" + a + a + "" + b);
```
1020101020
30101020
302010
10202010

Answer

30101020
Given a Calculator class with a method addAndPrint that takes two integer parameters, adds them, and prints the result, what will be the return value of the given method call in the following code snippet?
```
Calculator calc = new Calculator();
calc.addAndPrint(7, 5);
```
12
75
Compilation error
0

Answer

12
Given a Printer class with a method printGreeting that takes a String parameter and prints a greeting message including the provided name, what will be the return value of the given method call in the following code snippet?
```
Printer printer = new Printer();
printer.printGreeting("Alice");
```
Hello, Alice!
Hello, name!
Alice
Compilation error

Answer

Hello, Alice!
What is the variable name in the following declaration?
```
Car myCar = new Car("Toyota");
```
Car
myCar
new
Toyota

Answer

myCar
What is the type of the variable in the following declaration?
```
double price = 19.99;
```
double
price
19.99

Answer

double
What is the initial value of the variable in the following declaration?
```
boolean isActive = true;
```
boolean
isActive
true
there is no initial value

Answer

true
What is the value of result after the following sequence of statements?
```
int result = 5;
result = result + 10;
result = result - 3;
```
5
12
15
17

Answer

12

Identify the mistakes in the following variable declarations:

Answer

var y = "Hello"; and int y = 10; // have the same variable name y.
float pi = 3.14 // is missing a semicolon at the end.
String name = 'John'; // should use double quotes for the string value: String name = "John";.
age = 30; // is missing the type declaration.
int number; // is declared but not initialized.

Which of the following are valid variable names in Java?
name
_age
float
2ndPlace
$amount
public
accountBalance

Answer

name
_age
$amount
accountBalance
Choose the best variable name to hold the radius of a circle:
r
rad
circleRadius
radius
R

Answer

radius
What is the return type of the getArea() method of the Circle class? If unsure, check its method definition.
int
double
float
void

Answer

double
Assume Circle object is created with x, y, and raius. What does the following sequence of statements print?
```
Circle c = new Circle(10, 20, 15);
c.moveHorizontal(30);
System.out.println(c.getX());
```
10
30
40
50

Answer

40

What does this program print?

public class Demo
{
   public static void main(String[] args)
   {
      System.out.print("Hello");
      System.out.print(" ");
      System.out.print("World");
      System.out.println("!");
   }
}

Answer

Hello World!

Creating a Square Using Rectangle
```
Rectangle square = new Rectangle(0, 0, 50, 50);
square.setColor(Color.BLUE);
square.fill();
square.translate(10, 10);
```
Where will the square be positioned after executing this code?

At (0, 0)
At (10, 10)
At (50, 50)
At (60, 60)

Answer

At (10, 10)
Calling Methods on Different Objects
```
Rectangle rect = new Rectangle(10, 20, 30, 40);
Circle circ = new Circle(15, 25, 20);
rect.translate(5, 5);
circ.setColor(Color.GREEN);
```
What are the new properties of rect and circ after executing the code?

Rectangle at (10, 20) with no color, Circle at (15, 25) with no color
Rectangle at (15, 25) with no color, Circle at (15, 25) with no color
Rectangle at (10, 20) with no color, Circle at (15, 25) with color GREEN
Rectangle at (15, 25) with no color, Circle at (15, 25) with color GREEN

Answer

Rectangle at (15, 25) with no color, Circle at (15, 25) with color GREEN
Result of Executing Methods
```
Rectangle rect = new Rectangle(0, 0, 100, 100);
rect.setColor(Color.RED);
rect.translate(50, 50);
rect.grow(20, 20);
rect.fill();
```
What will be the final state of the rectangle?

Rectangle at (0, 0) with width 100, height 100, and color RED
Rectangle at (50, 50) with width 100, height 100, and color RED
Rectangle at (50, 50) with width 140, height 140, and color RED
Rectangle at (70, 70) with width 140, height 140, and color RED

Answer

Rectangle at (50, 50) with width 140, height 140, and color RED
Effect of translate Method on Coordinates
```
Line line1 = new Line(0, 0, 10, 10);
line1.translate(5, 5);
```
What will be the new coordinates of line1?

(0, 0) to (10, 10)
(5, 5) to (15, 15)
(0, 0) to (5, 5)
(10, 10) to (20, 20)

Answer

(5, 5) to (15, 15)
Invoking Multiple Methods on an Object
```
Rectangle rect = new Rectangle(10, 10, 20, 20);
rect.translate(10, 0);
rect.grow(5, 5);
```
What will be the new properties of the rectangle?

Rectangle at (10, 10) with width 20, height 20
Rectangle at (20, 10) with width 25, height 25
Rectangle at (20, 10) with width 30, height 30
Rectangle at (15, 15) with width 25, height 25

Answer

Rectangle at (20, 10) with width 30, height 30
Creating and Manipulating a Line Object
```
Line line1 = new Line(0, 0, 50, 50);
line1.setColor(Color.BLUE);
line1.translate(20, 20);
line1.draw();
```
Where will the line be drawn after executing this code?

From (0, 0) to (50, 50)
From (20, 20) to (70, 70)
From (20, 20) to (50, 50)
From (10, 10) to (60, 60)

Answer

From (20, 20) to (70, 70)
Result of Executing setSize and setColor Methods
```
Rectangle rect = new Rectangle(10, 20, 30, 40);
rect.setColor(Color.RED);
rect.setSize(50, 60);
rect.fill();
```
What will be the final properties of the rectangle?

Rectangle at (10, 20) with width 30, height 40, and color RED
Rectangle at (10, 20) with width 50, height 60, and color RED
Rectangle at (10, 20) with width 50, height 60, and no color
Rectangle at (0, 0) with width 50, height 60, and color RED

Answer

Rectangle at (10, 20) with width 50, height 60, and color RED
Creating a Rectangle Object
```
Rectangle rect = new Rectangle(10, 20, 30, 40);
rect.setColor(Color.RED);
rect.fill();
```
What will be the result of executing this code?

A rectangle with no color
A red rectangle filled with color
A rectangle with no fill
A blue rectangle filled with color

Answer

A red rectangle filled with color
Using Line and Rectangle Classes
```
Line line1 = new Line(10, 10, 50, 10);
Rectangle rect = new Rectangle(20, 20, 60, 30);
rect.translate(10, 10);
line1.translate(5, 0);
```
After the above code is executed, what are the new coordinates of line1 and rect respectively?

(15, 10, 55, 10) and (30, 30, 60, 30)
(15, 10, 50, 10) and (30, 30, 60, 30)
(15, 10, 55, 10) and (20, 20, 60, 30)
(10, 10, 50, 10) and (30, 30, 70, 40)

Answer

(15, 10, 50, 10) and (30, 30, 60, 30)
Combining Line and Rectangle
```
Line line1 = new Line(0, 0, 100, 0);
Line line2 = new Line(0, 100, 100, 100);
Rectangle rect = new Rectangle(50, 50, 20, 20);
line1.translate(0, 50);
line2.translate(0, -50);
rect.translate(-30, 30);
```
Which statement is true after the code execution?

Both lines will be at y=50 and y=50 respectively.
The rectangle will be at (20, 80).
The rectangle will be at (50, 20).
Both lines will remain at y=0 and y=100 respectively.

Answer

The rectangle will be at (20, 80).
Creating a Crate Design Using Line and Rectangle
```
Rectangle base = new Rectangle(10, 10, 100, 50);
Line line1 = new Line(10, 10, 110, 10);
Line line2 = new Line(10, 60, 110, 60);
base.setColor(Color.BROWN);
base.fill();
line1.setColor(Color.BLACK);
line2.setColor(Color.BLACK);
line1.translate(0, 25);
```
What does the crate look like after executing the code?

A brown rectangle with a black line in the middle.
A brown rectangle with a black line at the bottom.
A brown rectangle with a black line at the top.
A brown rectangle without any lines.

Answer

A brown rectangle with a black line in the middle.
Using Print and Println
```
System.out.print("Hello");
System.out.println("World");
System.out.println(3 + 4);
System.out.print("3 + 4");
```
What will be the output of this code?

HelloWorld73 + 4
HelloWorld
7
3 + 4
Hello World 7
Hello World
7 3 + 4

Answer

HelloWorld
7
3 + 4

Using String Methods

String s = "OpenAI";
System.out.print(s.charAt(2) + " ");
System.out.print(s.length() + " ");
System.out.print(s.substring(1, 4) + " ");
System.out.print(s.toUpperCase());

What will be the output of this code?

Answer

e 6 pen OPENAI

Combining String Methods
```
String s = "Hello World";
s = s.replace("World", "Java");
System.out.print(s.substring(0, 5) + " ");
System.out.println(s.toUpperCase());
```
What will be the output of this code?

Hello HELLO JAVA
Hello HELLO WORLD
World HELLO JAVA
Hello HELLO WORLD JAVA

Answer

Hello HELLO JAVA

Identify Error Types

public class Test {
    public static void main(String[] args) {
        int a = 10;
        int b = 0;
        System.out.println(a / b);
        System.out.println("End of program");
    }
}

What type of error will occur when this code is executed?

Answer

Runtime error (ArithmeticException)

Printing Expressions and Strings
```
System.out.print("The result of 2 + 3 is ");
System.out.println(2 + 3);
System.out.println("2 + 3");
```
What will be the output of this code?

The result of 2 + 3 is 2 + 3
The result of 2 + 3 is 5
The result of 2 + 3 is 5
2 + 3
The result of 2 + 3 is 5
5

Answer

The result of 2 + 3 is 5
2 + 3

Slightly harder MCQs

Printing Statements and Combining Strings
```
String s1 = "3 + 4";
int a = 3;
int b = 4;
System.out.println(s1);
System.out.println(a + b);
System.out.println("Result: " + a + b);
System.out.println("Result: " + (a + b));
```
What will be the output of this code?

3 + 4 7 Result: 34 Result: 34
3 + 4 7 Result: 7 Result: 7
3 + 4 7 Result: 34 Result: 7
3 + 4 34 Result: 34 Result: 7

Answer

3 + 4 7 Result: 34 Result: 7
Using Rectangle and Line Classes
```
Rectangle rect1 = new Rectangle(20, 20, 40, 40);
Line line1 = new Line(20, 20, 60, 20);
rect1.translate(10, 10);
line1.translate(5, 0);
```
What are the new coordinates of rect1 and line1 respectively?

(20, 20, 40, 40) and (25, 20, 65, 20)
(30, 30, 40, 40) and (25, 20, 60, 20)
(20, 20, 50, 50) and (25, 20, 65, 20)
(30, 30, 40, 40) and (20, 20, 60, 20)

Answer

(30, 30, 40, 40) and (25, 20, 60, 20)
Creating and Translating a Line Object
```
Line line = new Line(0, 0, 100, 0);
line.translate(50, 50);
```
What are the new coordinates of the line after translation?

(0, 0, 100, 50)
(50, 50, 150, 50)
(50, 50, 100, 0)
(0, 0, 50, 50)

Answer

(50, 50, 150, 50)
Creating and Translating a Square Using Rectangle
```
Rectangle square = new Rectangle(0, 0, 30, 30);
square.setColor(Color.GREEN);
square.translate(20, 20);
square.fill();
```
What will be the final position and color of the square?

(0, 0) and GREEN
(20, 20) and GREEN
(30, 30) and BLUE
(20, 20) and RED

Answer

(20, 20) and GREEN
Using String Methods and Printing
```
String str = "Java Programming";
System.out.println(str.charAt(5));
System.out.println(str.substring(0, 4));
System.out.println(str.replace("Java", "C++"));
```
What will be the output of this code?

a Java C++ Programming
P Java C++ Programming
P rogramming C++ Programming
a Java C++ rogramming

Answer

P Java C++ Programming