Question

Please help me to answer the 5 programming questions and give some specific explanations, thanks a lot !!!

Question Consider a class hierarchy that includes a class called Creature, with subclasses called Unicorn and Dragon. The Creature class has a method called feelsLike, Not yet answered which is overridden in the Unicorn and Dragon class. Marked out of The feelsLike method of the Creature class returns "smooth", while the feelsLike method is overridden in the Unicorn class to return "fluffy" and feels Like method 3.00 is overriden in the Dragon to return "scaly" Flag question What is the output of the following snippet of code? Explain your answer. If there is an error, how would you fix it? ArrayList c = new Array List ( ) ; c.add(new Unicorn ( ) ) ; c.add(new Creature () ) ; c.add(new Dragon ( ) ) ; m.get(m.size) . feels Like ( ) ); System.out.println ("Last creature goes В 1 A E Question 2 You have been tasked with writing a program that expects user input and, as always users do not always enter the right sort of information. As a consequence Not vet answered some of the code you have written will cause some methods calls to throw exceptions. Some of these methods throw unchecked exceptions whilst others return an invalid value (e.g. -1 or null). What is the differences between a checked and unchecked exception? Why do some methods return invalid values rather than Marked out of throwing an exception? 3.00 PFlag question AA Question 3 Given the following class: Not yet answered public class Utility Marked out of 3.00 / The method returns true if the ArrayList contains the String value, false otherwise arr Flag question Throws a Null PointerException if the ArrayList arr is null public boolean hasValue(Array List arr, String value) throws Nul1 Pointer Exception # code omitted Complete the following test code so that it thoroughly tests the method hasValue so it behaves as described. ALSO, explain your choice of tests. public class Utility Test @Test public void testHasValue complete this test method, making use of asssert method like assertEquals(...,.. .) AA B I Question 4 Why does Trent thinks that this cartoon is funny? Discuss in your answer the different tasks associated with using a version control system. Not yet answered Marked out of JIM, COULD YOU COME То ME FOR A МОMENT? 3.00 P Flag question OF COURSE WHAT'S UP? NOTHING, THANKS! JUST WANTED TO MAKE SURE THAT I'M THE FIRST TO CHECK IN THE FILES WE'VE BOTH EDITED СНАРТER 1: НOW TO AVOID MERGE CONFLICTS Question 5 In the following method, describe which variables are thread-safe and which are not thread-safe and why. Not yet answered public int wasSoHard (int x, String in, Array List stuff) { Marked out of char c in.charAt (x) 3.00 P Flag question for (int i= 0; i

Answer 1

1.

The output of this code is:

"scaly"

This is because the feelslike() method of class Dragon() get called.

2.

Checked: are the exceptions that are checked at compile time. If some code within a method throws a checked exception, then the method must either handle the exception or it must specify the exception using throws keyword.

For example, consider the following Java program that opens file at location “C:\test\a.txt” and prints the first three lines of it. The program doesn’t compile, because the function main() uses FileReader() and FileReader() throws a checked exception FileNotFoundException. It also uses readLine() and close() methods, and these methods also throw checked exception IOException

import java.io.*;

class Main {
   public static void main(String[] args) {
       FileReader file = new FileReader("C:\\test\\a.txt");
       BufferedReader fileInput = new BufferedReader(file);
      
       // Print first 3 lines of file "C:\test\a.txt"
       for (int counter = 0; counter < 3; counter++)
           System.out.println(fileInput.readLine());
      
       fileInput.close();
   }
}

Output:

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - 
unreported exception java.io.FileNotFoundException; must be caught or declared to be 
thrown
    at Main.main(Main.java:5)

To fix the above program, we either need to specify list of exceptions using throws, or we need to use try-catch block. We have used throws in the below program. Since FileNotFoundException is a subclass of IOException, we can just specify IOException in the throws list and make the above program compiler-error-free.

import java.io.*;

class Main {
   public static void main(String[] args) throws IOException {
       FileReader file = new FileReader("C:\\test\\a.txt");
       BufferedReader fileInput = new BufferedReader(file);
      
       // Print first 3 lines of file "C:\test\a.txt"
       for (int counter = 0; counter < 3; counter++)
           System.out.println(fileInput.readLine());
      
       fileInput.close();
   }
}

Unchecked are the exceptions that are not checked at compiled time. In C++, all exceptions are unchecked, so it is not forced by the compiler to either handle or specify the exception. It is up to the programmers to be civilized, and specify or catch the exceptions.
In Java exceptions under Error and RuntimeException classes are unchecked exceptions, everything else under throwable is checked.

Consider the following Java program. It compiles fine, but it throws ArithmeticException when run. The compiler allows it to compile, because ArithmeticException is an unchecked exception.

class Main {
public static void main(String args[]) {
   int x = 0;
   int y = 10;
   int z = y/x;
}
}

Since exceptions, if not caught properly, result in run time failure, some programmers prefer returning an invalid value.

NOTE: As per HOMEWORKLIB POLICY, I am allowed to answer only 2 questions (including sub-parts) on a single post. Kindly post the remaining questions separately and I will try to answer them. Sorry for the inconvenience caused.