JAVA MCQ: JAVA Multiple Choice Questions and Answers

What method signature will work with this code?

boolean healthyOrNot = isHealthy("avocado");

Add a Duck called "Waddles" to the ArrayList ducks.

public class Duck {
  private String name;
  Duck(String name) {}
}

If you encounter UnsupportedClassVersionError it means the code was **\_** on a newer version of Java than the JRE **\_** it.

Which keyword lets you use an interface?

What code would you use to tell if "schwifty" is of type String?

Which operator would you use to find the remainder after division?

Which are valid keywords in a Java module descriptor (module-infoJava)?

What is the result of this code?

class Main {
    public static void main (String[] args){
        System.out.println(print(1));
    }
    static Exception print(int i){
        if (i>0) {
            return new Exception();
        } else {
            throw new RuntimeException();
        }
    }
}

What type of variable can be assigned to only once?

What is the result of this code?

1: class Main {
2: 		Object message(){
3: 			return "Hello!";
4: 		}
5: 		public static void main(String[] args) {
6: 			System.out.print(new Main().message());
7: 			System.out.print(new Main2().message());
8: 		}
9: }
10: class Main2 extends Main {
11: 	String message(){
12: 		return "World!";
13: 	}
14: }

Which type of variable keeps a constant value once it is assigned?

What does the following code print?

String str = "abcde";
str.trim();
str.toUpperCase();
str.substring(3, 4);
System.out.println(str);

You have an ArrayList of names that you want to sort alphabetically. Which approach would NOT work?

Which keyword lets you call the constructor of a parent class?

What is the result of this code?

try {
    System.out.println("Hello World");
} catch (Exception e) {
    System.out.println("e");
} catch (ArithmeticException e) {
    System.out.println("e");
} finally {
    System.out.println("!");
}

How can you achieve runtime polymorphism in Java?

What is the output of this code?

class Main {
    public static void main(String[] args){
        int a = 123451234512345;
        System.out.println(a);
    }
}

What does this code print?

System.out.print("apple".compareTo("banana"));

How does the keyword _volatile_ affect how a variable is handled?

What does this code print?

public static void main(String[] args) {
    int x=5,y=10;
    swapsies(x,y);
    System.out.println(x+"="+y);
}

static void swapsies(int a, int b) {
    int temp=a;
    a=b;
    b=temp;
}

Fill in the blank to create a piece of code that will tell whether int0 is divisible by 5: 

boolean isDivisibleBy5 = _____

Which is the most reliable expression for testing whether the values of two string variables are the same?

What is the output of this code?

class Main {
  public static void main(String[] args) {
    String message = "Hello";
    print(message);
    message += "World!";
    print(message);
  }
  static void print(String message){
    System.out.print(message);
    message += " ";
  }
}

What is the result of this code?

1: int a = 1;
2: int b = 0;
3: int c = a/b;
4: System.out.println(c);

What is a valid use of the hashCOde() method?

Which letters will print when this code is run?

public static void main(String[] args) {
  try {
    System.out.println("A");
    badMethod();
    System.out.println("B");
  } catch (Exception ex) {
    System.out.println("C");
  } finally {
    System.out.println("D");
  }
}
public static void badMethod() {
  throw new Error();
}

Why are ArrayLists better than arrays?

How many times will this code print "Hello World!"?

class Main {
    public static void main(String[] args){
        for (int i=0; i<10; i=i++){
            i+=1;
            System.out.println("Hello World!");
        }
    }
}

Given the following definitions, which of these expressions will NOT evaluate to true?

boolean b1 = true, b2 = false; int i1 = 1, i2 = 2;

Which statement is NOT true?

Declare and initialize an array of 10 ints.

How would you fix this code so that it compiles?

public class Nosey {
  int age;
  public static void main(String[] args) {
    System.out.println("Your age is: " + age);
  }
}

Which choice is a disadvantage of inheritance?

eclare a variable that holds the first four digits of Π

What is displayed when this code is compiled and executed?

public class Main {
  public static void main(String[] args) {
    int x = 5;
    x = 10;
    System.out.println(x);
  }
}

Given the following two classes, what will be the output of the Main class?

package mypackage;
public class Math {
    public static int abs(int num){
        return num < 0 ? -num : num;
    }
}
package mypackage.elementary;
public class Math {
    public static int abs (int num) {
        return -num;
    }
}

import mypackage.Math;
import mypackage.elementary.*;

class Main {
    public static void main (String args[]){
        System.out.println(Math.abs(123));
    }
}

How many times f will be printed?

public class Solution {
    public static void main(String[] args) {
        for (int i = 44; i > 40; i--) {
            System.out.println("f");
        }
    }
}

What kind of relationship does "extends" denote?

What is the output of this code?

import java.util.*;
class Main {
  public static void main(String[] args) {
    List<Boolean> list = new ArrayList<>();
    list.add(true);
    list.add(Boolean.parseBoolean("FalSe"));
    list.add(Boolean.TRUE);
    System.out.print(list.size());
    System.out.print(list.get(1) instanceof Boolean);
  }
}

Which functional interfaces does Java provide to serve as data types for lambda expressions?

What is the output of this code?

class Main {
    public static void main (String[] args) {
        List list = new ArrayList();
        list.add("hello");
        list.add(2);
        System.out.print(list.get(0) instanceof Object);
        System.out.print(list.get(1) instanceof Integer);
    }
}

What is a valid use of the hashCode() method?

Given this code, which command will output "2"?

class Main {
    public static void main(String[] args) {
        System.out.println(args[2]);
    }
}

The runtime system starts your program by calling which function first?

Java programmers commonly use design patterns. Some examples are the __, which helps create instances of a class, the __, which ensures that only one instance of a class can be created; and the __, which allows for a group of algorithms to be interchangeable.

What statement returns true if "nifty" is of type String?

What is the result of this code?

1: class MainClass {
2:  final String message(){
3:      return "Hello!";
4:  }
5: }

6: class Main extends MainClass {
7:  public static void main(String[] args) {
8:      System.out.println(message());
9:  }

10: String message(){
11:     return "World!";
12:  }
13: }

What can you use to create new instances in Java?

What will this program print out to the console when executed?

import java.util.LinkedList;

public class Main {
    public static void main(String[] args){
        LinkedList<Integer> list = new LinkedList<>();
        list.add(5);
        list.add(1);
        list.add(10);
        System.out.println(list);
    }
}

Using Java's Reflection API, you can use __ to get the name of a class and __ to retrieve an array of its methods.

What language construct serves as a blueprint containing an object's properties and functionality?

What is an IS-A relationship?

How do you write a foreach loop that will iterate over ArrayList<Pencil>pencilCase?

How would you convert a String to an Int?

Object-oriented programming is a style of programming where you organize your program around __ rather than __ and data rather than logic.

What method can be used to create a new instance of an object?

What is the output of this code?

class Main {
    public static void main(String[] args){
       String message = "Hello";
       for (int i = 0; i<message.length(); i++){
          System.out.print(message.charAt(i+1));
       }
    }
}

How do you force an object to be garbage collected?

Which is the most up-to-date way to instantiate the current date?

You get a NullPointerException. What is the most likely cause?

What is the output of this code?

import java.util.*;
class Main {
  public static void main(String[] args) {
    String[] array = {"abc", "2", "10", "0"};
    List<String> list = Arrays.asList(array);
    Collections.sort(list);
    System.out.println(Arrays.toString(array));
  }
}

Which access modifier makes variables and methods visible only in the class where they are declared?

What is the output of this code?

1: class Main {
2:   public static void main (String[] args) {
3:     int array[] = {1, 2, 3, 4};
4:     for (int i = 0; i < array.size(); i++) {
5:        System.out.print(array[i]);
6:     }
7:   }
8: }

Which of the following can replace the CODE SNIPPET to make the code below print "Hello World"?

interface Interface1 {
    static void print() {
        System.out.print("Hello");
    }
}

interface Interface2 {
    static void print() {
        System.out.print("World!");
    }
}

Use the magic power to cast a spell

public class MagicPower {
    void castSpell(String spell) {}
}

What is not a java keyword

Given the string "strawberries" saved in a variable called fruit, what would fruit.substring(2, 5) return?

What is the result of this code?

char smooch = 'x';
System.out.println((int) smooch);

Refactor this event handler to a lambda expression:

groucyButton.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Press me one more time..");
    }
});

What is the result of this code?

try{
    System.out.print("Hello World");
}catch(Exception e){
    System.out.println("e");
}catch(ArithmeticException e){
    System.out.println("e");
}finally{
    System.out.println("!")
}

By implementing encapsulation, you cannot directly access the class's _ properties unless you are writing code inside the class itself.

Which statements about abstract classes are true?

1. They can be instantiated.
2. They allow member variables and methods to be inherited by subclasses.
3. They can contain constructors.

What is the output of this code?

class Main {
  static int count = 0;
  public static void main(String[] args) {
    if (count < 3) {
      count++;
      main(null);
    } else {
      return;
    }
    System.out.println("Hello World!");
  }
}

What is the output of this code?

class Main {
    public static void main (String[] args) {
        String message = "Hello world!";
        String newMessage = message.substring(6, 12)
            + message.substring(12, 6);
        System.out.println(newMessage);
    }
}

Normally, to access a static member of a class such as Math.PI, you would need to specify the class "Math". What would be the best way to allow you to use simply "PI" in your code?