Question

Java programming only

Create a Java program that inputs a grade from the user. The grade input from the user will be an integer. Once the input is stored, use an if-else-if block of code to determine the letter grade of the inputted integer grade. Do not use a bunch of if statements by themselves to solve this problem. You will print an error message for inputs greater than 100 and for inputs less than 0. Both errors must be handled together by a compound conditional statement that is joined by a short circuit AND or OR operator. Assign your error message to a String variable and use that variable in a System.out.println statement to print the error. You must assign a char variable for each letter grade. Use System.out.printf to print the letter grade.

Run your program several times using these inputs and ensure that you are receiving these outputs:

• input: 140
  • expected output: ERROR - You have entered an invalid input.
• Input: -42
  • expected output: ERROR - You have entered an invalid input.
• input: 85
  • expected output: You have earned the letter grade B.

Run it a few more times using various other inputs.

Part II

Convert the if-else-if code block to a switch statement to solve the problem. Use modulus and/or integer division to convert the grade input so that the range of grades are converted to one value. All other requirements from Part I are still required for part two. Use the same inputs and the outputs should remain the same.

Part III

Write describing why you should not use if statements alone to solve part I and why using if-else-if statements is a better technique. Think about the differences between these two selection structures and why the latter might be preferred for this particular solution.

Part IV

Section 3.15 in your zyBook says, "Strings are considered immutable, meaning they cannot be changed." Do a little research on what this means and on how Strings are handled in memory in Java. Using words and/or a diagram, explain what you've learned and why strings are immutable.

Answer 1

Note: Could you plz go through this code and let me know if u need any changes in this.Thank You
_________________

// Part 1:

import java.util.Scanner;

public class GradeLetter {

   public static void main(String[] args) {
       int num;
String mesg="";
char gradeLetter = 0;
       /*
       * Creating an Scanner class object which is used to get the inputs
       * entered by the user
       */
       Scanner sc = new Scanner(System.in);
       while(true)
       {
           System.out.print("input: ");
           num=sc.nextInt();
          
           if(num<0 || num>100)
           {
               mesg="ERROR - You have entered an invalid input.";
              
           }
           else
           {
               if (num >= 90)
                   gradeLetter = 'A';
                   else if (num >= 80 && num < 90)
                   gradeLetter = 'B';
                   else if (num >= 70 && num < 80)
                   gradeLetter = 'C';
                   else if (num >= 60 && num < 70)
                   gradeLetter = 'D';
                   else if (num < 60)
                   gradeLetter = 'F';
              
               break;
           }  
           System.out.println(mesg);
       }
      
       System.out.printf("You have earned the letter grade %c.",gradeLetter);
   }

}

_________________________

output:

input: 140
ERROR - You have entered an invalid input.
input: -42
ERROR - You have entered an invalid input.
input: 85
You have earned the letter grade B.

__________________________

2)

// using Switch

import java.util.Scanner;

public class GradeLetterSwitch {

   public static void main(String[] args) {
       int num;
       String mesg = "";
       char gradeLetter = 0;
       /*
       * Creating an Scanner class object which is used to get the inputs
       * entered by the user
       */
       Scanner sc = new Scanner(System.in);
       while (true) {
           System.out.print("input: ");
           num = sc.nextInt();

           if (num < 0 || num > 100) {
               mesg = "ERROR - You have entered an invalid input.";

           } else {
               num /= 10;
               switch (num) {
               case 10:
               case 9: {
                   gradeLetter = 'A';
                   break;
               }
               case 8: {
                   gradeLetter = 'B';
                   break;
               }
               case 7: {
                   gradeLetter = 'C';
                   break;
               }
               case 6: {
                   gradeLetter = 'D';
                   break;
               }
               case 5: {
                   gradeLetter = 'F';
                   break;
               }

               }

               break;
           }
           System.out.println(mesg);
       }

       System.out.printf("You have earned the letter grade %c.", gradeLetter);

   }

}

_________________________

output:

input: 140
ERROR - You have entered an invalid input.
input: -42
ERROR - You have entered an invalid input.
input: 85
You have earned the letter grade B.

__________________________

3)

If we are using multiple IF statements , if we want to use a condition like if(num<100).Then for the numbers like 95 or 79 or 65 ,the if condition will get executed like that there can be a chance that more that one if condition is executed.The we may get incorrect output.

But if we use If-Else-If block only one condition will be executed.Then we may get the exact output.

__________________________

4)

4) String objects are Immutable, meaning they can’t grow or shrink.

Immutable:

We can modify the content of the String object.

i.e if we have a string object which contains some content inside it.If we want to append some date to that existing string content.Then it is not possible to append.

If we try to append by using concat operator(+),then a new String object is created with that new content.Previous reference variable stops referencing the old String Object and start referencing the newly created String object.

String str1=”hi”;//A string object contains the content “hi” which is referenced by str1 reference variable.

System.out.println(st1+” Kane”);//Here a new String object is created which contains the content “hi Kane” which is pointed by the reference variable str1.The previous string object don’t have any reference variable now.Which will be removed by the garbage collector.

_______________Could you plz rate me well.Thank You