CODEWITHSUNDEEP
java
jjason89
jjason89

Reputation: 39

for loop structure

This program will calculate the average grade for 4 exams using a for loop by prompting the user for exam grades, one at a time, then calculate the average and display the result. 

public class ExamsFor4 {

public static void main(String[] arguments) {


int inputNumber; // One of the exams input by the user.
int sum = 0;     // The sum of the exams.
int i;       // Number of exams.
Double Avg;      // The average of the exams.

TextIO.put("Please enter the first exam: ");        // get the first exam.
inputNumber = TextIO.getlnInt();    

for ( i = 1; i <= 4; i++ ) {  

    sum += inputNumber;                 // Add inputNumber to running sum.
    TextIO.put("Please enter the next exam: ");     // get the next exam.   
    inputNumber = TextIO.getlnInt();

        if (i == 4) {
            Avg = ((double)sum) / i;
            TextIO.putln();
            TextIO.putln("The total sum for all " + i +" exams is " + sum);
            TextIO.putf("The average for the exams entered is %1.2f.\n", Avg);
            break;

        }
} 

}   // end main ()
}  // end class ExamsFor4

My result:

Please enter the first exam: 100
Please enter the next exam: 99
Please enter the next exam: 98
Please enter the next exam: 97
Please enter the next exam: 96
The total sum for all 4 exams is 394
The average for the exams entered is 98.50.

This would be correct except for the last print out of: 'Please enter the next exam: 96' I tried putting the IF statement between the 'sum' line and the TextIO.put 'Enter next exam', but that isolates it.

Thanks, from a Network Dude trap in a Programmer's world.

Upvotes: 1

Views: 1328

Answers (5)

Alex
Alex

Reputation: 17

import java.util.Scanner;
public class ExamsFor4 {

public static void main(String[] arguments) {

    int sum = 0; // The sum of the exams.
    int i = 1; // Number of exams.
    double avg = 0; // The average of the exams.

    Scanner in = new Scanner(System.in);
    System.out.print("Please enter the first exam: ");
    sum += in.nextInt();
    i++;
    while(i<=4){
        System.out.print("Please enter the next exam: ");
        sum += in.nextInt();
        if(i==4)
            break;// this line is so that it wont increment an extra time.
        i++;
    }
    System.out.println("The total sum for all " + i +" exams is " + sum);
    avg = ((double)sum/i);
    System.out.println("The average for the exams entered is" + avg);
} // end main ()
} // end class ExamsFor4

Upvotes: 0

YoK
YoK

Reputation: 14505

Just making few changes in your code makes it work. But you should follow cleaner approach as proposed in some of answers.

public class ExamsFor4 {

  public static void main(String[] arguments) {
    int inputNumber; // One of the exams input by the user.
    int sum = 0;     // The sum of the exams.
    int i;       // Number of exams.
    double Avg;      // The average of the exams.

    TextIO.put("Please enter the first exam: ");        // get the first exam.
    inputNumber = TextIO.getlnInt();    
    sum += inputNumber;

    for ( i = 1; i < 4; i++ ) {  

      TextIO.put("Please enter the next exam: ");     // get the next exam.   
      inputNumber = TextIO.getlnInt();
      sum += inputNumber;                 // Add inputNumber to running sum.

    } 

    Avg = ((double)sum) / i;
    TextIO.putln();
    TextIO.putln("The total sum for all " + i +" exams is " + sum);
    TextIO.putf("The average for the exams entered is %1.2f.\n", Avg);

  }   // end main ()
}  // end class ExamsFor4

Upvotes: 0

polygenelubricants
polygenelubricants

Reputation: 383746

You have what is called an off-by-one error, compounded by the fact that you're convoluting your loop logic unnecessarily.

With regards to the loop, I recommend two things:

  • Don't loop for (int i = 1; i <= N; i++); it's atypical
    • Do for (int i = 0; i < N; i++); it's more typical
  • Instead of checking for the last iteration to do something, refactor and take it outside of the loop

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See also

On Double Avg

In Java, variable names start with lowercase. Moreover, Double is a reference type, the box for the primitive double. Whenever possible, you should prefer double to Double

See also

Related questions

Rewrite

Here's a way to rewrite the code that makes it more readable. I used java.util.Scanner since I don't think TextIO is standard, but the essence remains the same.

import java.util.*;

public class ExamsFor4 {
    public static void main(String[] arguments) {
        Scanner sc = new Scanner(System.in);
        final int NUM_EXAMS = 4;
        int sum = 0;

        for (int i = 0; i < NUM_EXAMS; i++) {
            System.out.printf("Please enter the %s exam: ",
                (i == 0) ? "first" : "next"
            );
            sum += sc.nextInt();
        }
        System.out.printf("Total is %d%n", sum);
        System.out.printf("Average is %1.2f%n", ((double) sum) / NUM_EXAMS);
    }
}

An example session is as follows:

Please enter the first exam: 4
Please enter the next exam: 5
Please enter the next exam: 7
Please enter the next exam: 9
Total is 25
Average is 6.25

Note that:

  • Only necessary variables are declared
    • The loop index is local only to the loop
  • There are no cluttering comments
    • Instead, focus on writing clear, concise, readable code
  • If it makes sense to make something final, do so
    • Constants in Java is all uppercase

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Upvotes: 12

Burbas
Burbas

Reputation: 803

You should probably put the if-statment outside the for-loop. That way you don't need the if-statement. Second the statement in the loop should be < 4 instead of <= 4. 

public class ExamsFor4 {

public static void main(String[] arguments) {


int inputNumber; // One of the exams input by the user.
int sum = 0;     // The sum of the exams.
int i;       // Number of exams.
Double Avg;      // The average of the exams.

TextIO.put("Please enter the first exam: ");        // get the first exam.
inputNumber = TextIO.getlnInt();    

for ( i = 1; i < 4; i++ ) {  

    sum += inputNumber;                 // Add inputNumber to running sum.
    TextIO.put("Please enter the next exam: ");     // get the next exam.   
    inputNumber = TextIO.getlnInt();
} 

Avg = ((double)sum) / i;
TextIO.putln();
TextIO.putln("The total sum for all " + i +" exams is " + sum);
TextIO.putf("The average for the exams entered is %1.2f.\n", Avg);
break;

}   // end main ()
}

Upvotes: 0

ChrisF
ChrisF

Reputation: 137148

Change your end condition to be strictly less than 4 and put the code that prints out the total and average outside the loop.

Upvotes: 3

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