Java Assessment

Q1. Given the string "strawberries" saved in a variable called fruit, what would "fruit.substring(2, 5)" return?

rawb
raw <<<<---Correct
awb
traw

Reasoning: The substring method is accepting two arugments. The first argument being the index to start(includes that char at 2) and the second the index of the string to end the substring(excludes the char at 5). Strings in Java are like arrays of chars. Therefore the method will return "raw" as those are the chars in indexs 2,3, and 4. You can also take the ending index and subtract the beginning index from it, to determine how many chars will be included in the substring (5-2=3).

Q2. How can you achieve runtime polymorphism in Java?

method overloading
method overrunning
method overriding <<<<--- Correct
method calling

Q3. Given the following definitions, which of these expression will NOT evaluate to true?

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

(i1 | i2) == 3
i2 && b1 <<<<---Correct
b1 || !b2
(i1 ^ i2) < 4

Q4. What can you use to create new instances in Java?

constructor <<<<---Correct
another instance
field
private method

Q5. 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]);
       }
     }
   }

It will not compile because of line 4. <<<<---Correct
It will not compile because of line 3.
123
1234

Q6. Which of the following can replace the CODE SNIPPET to make the code below print "Hello World"?

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

super1.print(); super2.print();
this.print();
super.print();
Interface1.print(); Interface2.print();

Q7. What does the following code print?

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

CD
CDE
D
"abcde" <<<<---Correct

Q8. What is the result of this code?

1: class Main {
2:   public static void main (String[] args){
3:     System.out.println(print(1));
4:   }
5:   static Exception print(int i){
6:       if (i>0) {
7:          return new Exception();
8:       } else {
9:          throw new RuntimeException();
10:      }
11:  }
12: }

It will show a stack trace with a runtime exception.
"java.lang.Exception" <<<<---Correct
It will run and throw an exception.
It will not compile.

Q9. Which class can compile given these declarations?

1: interface One {
2:      default void method() {
3:          System.out.println(""One"");
4:      }   }
5: interface Two {
6:      default void method () {
7:          System.out.println(""One"");
8:      }   }

  class Three implements One, Two {
    publc void method() {
        super.One.method();
  } }

  class Three implements One, Two {
    publc void method() {
        One.method();
  } }

class Three implements One, Two {
}

<------ correct

  class Three implements One, Two {
    publc void method() {
        One.super.method();
  } }

Q10. What is the output of this code?

1: class Main {
2:  public static void main (String[] args) {
3:      List list = new ArrayList();
4:      list.add("hello");
5:      list.add(2);
6:      System.out.print(list.get(0) instanceof Object);
7:      System.out.print(list.get(1) instanceof Integer);
8:  }
9: }

The code does not compile.
truefalse
truetrue <<<<---Correct
falsetrue

Q11. 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;
    }
}
1: import mypackage.Math;
2: import mypackage.elementary.*;

3: class Main {
4:  public static void main (String args[]){
5:      System.out.println(Math.abs(123));
6:  }
7: }

Lines 1 and 2 generate compiler erros due to class name conflicts.
"-123"
It will throw an exception on line 5.
"123" <--- Correct // The answer is "123". The abs() method evaluates to the one inside mypackage.Math class.

Q12. 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: }

It will not compile because of line 10. <--- Correct
"Hello!"
It will not compile because of line 2.
"World!"

Q13. Given this code, which command will output "2"?

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

java Main 1 2 "3 4" 5
java Main 1 "2" "2" 5 <--- Correct
java Main.class 1 "2" 2 5
java Main 1 "2" "3 4" 5

Q14. What is the output of this code?

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

"123451234512345"
Nothing - this will not compile. <<<<---Correct
a negative integer value
"12345100000"

Reasoning: The int type in Java can be used to represent any whole number from -2147483648 to 2147483647. Therefore this code will not compile as the number assigned to 'a' is larger than the int type can hold.

Q15. 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);
    }
}

The code does not compile.
A runtime exception is thrown <<<<---Correct
"world!!world"
"world!world!"

String m = "Hello world!";
String n = m.substring(6,12) + m.substring(12,6);
System.out.println(n);

Q16. How do you write a foreach loop that will iterate over ArrayList<Pencil>pencilCase?

for (Pencil pencil : pencilCase) {} <<<<---Correct
for (pencilCase.next()) {}
for (Pencil pencil : pencilCase.iterator()) {}
for (pencil in pencilCase) {}

Q17. Fill in the blanks?

Object-oriented programming (OOP) is a programming language model that organizes software design around (objects), rather than (actions).

Q18. What code would you use to tell if "schwifty" is of type String?

"schwifty".getType() == String
"schwifty".getClass().getsimpleName() == "String"
"schwifty".getType().equals("String")
"schwifty" instanceof String <<<<---Correct

Q19. Correct output of `"apple".compareTo("banana")`

0
positive number
negative number <<<<---Correct
compilation error

Q20. You have an ArrayList of names that you want to sort alphabetically. Which approach would NOT work?

names.sort(Comparator.comparing(String::toString))
Collections.sort(names)
names.sort(List.DESCENDING) <<<--- Correct
names.stream().sorted((s1, s2) -> s1.compareTo(s2)).collect(Collectors.toList())

Q21. By implementing encapsulation, you cannot directly access the class's _ properties unless you are writing code inside the class itself.

private <<<<---Correct
protected
no-modifier
public

Q22. Which is the most up-to-date way to instantiate the current date?

new SimpleDateFormat("yyyy-MM-dd").format(new Date())
new Date(System.currentTimeMillis())
LocalDate.now()
Calender.getInstance().getTime() <<<<--- Correct

Q23. Fill in the blank to create a piece of code that will tell wether int0 is divisible by 5:

boolean isDivisibleBy5 = _____

int0 / 5 ? true: false
int0 % 5 == 0 <<<<---Correct
int0 % 5 != 5
Math.isDivisible(int0, 5)

Q24. How many time 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!");
        }
    }
}

10 times <<<<--- Correct
9 times
5 times
infinite number of times

Reason : Observe the loop increment. It's not an increment, it's an assignment(post).

Q25. The runtime system starts your program by calling which function first?

print
iterative
hello
main <<<<---Correct

Q26. 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("!")
}

It will throw a runtime exception
It will not compile <<<<---Correct
Hello World!
Hello World

Q27. Which statement is NOT true?

An anonymous class may specify an abstract base class as its base type.
An anonymous class does not require a zero-argument constructor. <<<<---Correct
An anonymous class may specify an interface as its base type.
An anonymous class may specify both an abstract class and interface as base types

Q28. What will this program print out to the console when executed?

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);
    }
}

[5, 1, 10] <<<<---Correct
[10, 5, 1]
[1, 5, 10]
[10, 1, 5]

Q29. 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));
       }
    }
}

"Hello"
A runtime exception is thrown. <<<<---Correct
The code does not compile.
"ello"

Q30. Object-oriented programming is a style of programming where you organize your program around rather than and data rather than logic.

functions; actions
objects; actions <<<<---Correct
actions; functions
actions; objects

Q31. What statement returns true if "nifty" is of type String?

"nifty".getType().equals("String")
"nifty".getType() == String
"nifty".getClass().getSimpleName() == "String"
"nifty" instanceof String <<<<---Correct

Q32. 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);
	}
}

A runtime exception is thrown.
3false
2true
3true <<<<---Correct

Q33. 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: }

It will not compile because of line 7.
Hello!Hello!
Hello!World! <<<<---Correct
It will not compile because of line 11.

Q34. What method can be used to create a new instance of an object?

another instance
field
constructor <<<<---Correct
private method

Q35. Which is the most reliable expression for testing whether the values of two string variables are the same?

string1 == string2
string1 = string2
string1.matches(string2)
string1.equals(string2) <<<<---Correct

Q36. 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();
}

A, B, and D
A, C, and D
C and D
A and D <<<<---Correct

Q37. 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!");
	}
}

It will throw a runtime exception.
It will not compile.
It will print "Hello World!" three times. <<<<---Correct
It will run forever.

Q38. 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));
	}
}

[abc, 0, 2, 10]
The code does not compile.
[abc, 2, 10, 0]
[0, 10, 2, abc] <<<<---Correct

Q39. 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 += " ";
	}
}

Hello World!
HelloHelloWorld! <<<<---Correct
Hello Hello World!
Hello HelloWorld!

Q40. 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);
	}
}

x
null
10 <<<<---Correct
5

Q41. Which approach cannot be used to iterate over a List named theList?

for (int i = 0; i < theList.size(); i++) {
    System.out.println(theList.get(i));
}

for (Object object : theList) {
    System.out.println(object);
}

Iterator it = theList.iterator();
for (it.hasNext()) {
    System.out.println(it.next());
}

<<<<---Correct

```
theList.forEach(System.out::println);
```

Q42. What method signature will work with this code?

boolean healthyOrNot = isHealthy("avocado");

public void isHealthy(String avocado)
boolean isHealthy(String string) <<<<---Correct
public isHealthy("avocado")
private String isHealthy(String food)

Q43. Which are valid keywords in a Java module descriptor (module-infoJava)?

provides, employs
imports, exports
consumes, supplies
requires, exports <<<<---Correct

Q44. Which type of variable keeps a constant value once it is assigned?

non-static
static
final <<<<---Correct
private

Q45. How does the keyword volatile affect how a variable is handled?

It will be read by only one thread at a time.
It will be stored on the hard drive.
It will never be cached by the CPU. <<<<---Correct
It will be preferentially garbage collected.

Q46. What is the result of this code?

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

an alphanumeric character
a negative number
a positive number <<<<---Correct
a ClassCastException

Q47. You get a NullPointerException. What is the most likely cause?

A file that needs to be opened cannot be found.
A network connection has been lost in the middle of communications.
Your code has used up all available memory.
The object you are using has not been instantiated. <<<<---Correct

Q48. 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);
	}
}

Make age static. <<<<---Correct
Make age global.
Make age public.
Initialize age to a number.

Q49. Add a Duck called "Waddles" to the ArrayList ducks.

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

Duck waddles = new Duck(); ducks.add(waddles);
Duck duck = new Duck("waddles"); ducks.add(wadd1es);
ducks.add(new Duck("waddles")); <<<<---Correct
ducks.add(new Waddles());

Q50. If you encounter `UnsupportedClassVersionError` it means the code was _ on a newer version of Java than the JRE _ it.

executed; interpreting
executed; compiling
compiled; executing <<<<--- Correct
compiled, translating

Q51. Given this class, how would you make the code compile?

public class TheClass {
	private final int x;
}

```
public TheClass() {
	x += 77;
}
```
```
public TheClass() {
	x = null;
}
```
```
public TheClass() {
	x = 77;
}
```
<<<<--- Correct

private void setX(int x) {
	this.x = x;
}
public TheClass() {
	setX(77);
}

Q52. 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");
		}
	}
}

4 <<<<---Correct
3
5
A Runtime exception will be thrown

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