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I'm having an awful time with arrays. I'm so confused. Can anyone lend some guidance to get me on track?
CODE
import java.util.Scanner; // Needed for Scanner class
/** This program uses a String array (or ArrayList object) to hold the names of 5 students, an array of 5 characters to hold the student's letter grades, and five arrays of 4 doubles each to hold their test scores.
Program allows user to enter each student's name and 4 test scores.
Program displays student's name, average test score and letter grade. */
public class GradeBook { public static void main(String[] args) { final int STUDENTS = 5;// Number of students final char LETTERS = 5; // Number of grades final int TESTS = 4; // Number of tests
// Create an array to hold students names. String[] names = new String[STUDENTS]; char[] grades = new char[LETTERS]; double[] score1 = new double[TESTS]; double[] score2 = new double[TESTS]; double[] score3 = new double[TESTS]; double[] score4 = new double[TESTS]; double total = 0; double average; for (int index = 0; index < score1.length; index++) total += score1[index]; average = total / score1.length; for (int index = 1; index < score1.length; index++) total += score2[index]; average = total / score1.length; for (int index = 2; index < score1.length; index++) total += score3[index]; average = total / score1.length; for (int index = 3; index < score1.length; index++) total += score4[index]; average = total / score1.length;
int count = 0;
// Create a Scanner object for keyboard input. Scanner keyboard = new Scanner(System.in);
// Get the names of each student. System.out.println("Enter student's name: "); String student = keyboard.nextLine(); System.out.println("Enter student's 1st test score: "); double test1 = Double.parseDouble(keyboard.nextLine()); System.out.println("Enter student's 2nd test score: "); double test2 = Double.parseDouble(keyboard.nextLine()); System.out.println("Enter student's 3rd test score: "); double test3 = Double.parseDouble(keyboard.nextLine()); System.out.println("Enter student's 4th test score: "); double test4 = Double.parseDouble(keyboard.nextLine()); {
public class GradeBook { public static void main(String[] args) { final int STUDENTS = 5;// Number of students final char LETTERS = 5; // Number of grades final int TESTS = 4; // Number of tests
// Create an array to hold students names. String[] names = new String[STUDENTS]; char[] grades = new char[LETTERS]; double[] scores = new double[TESTS];
Scanner input = new Scanner(System.in);
// Get the names of each student System.out.println("Enter student's name: "); String student = input.nextLine();
// Get student scores System.out.println("Insert 4 test scores:"); double[] scores = {input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble()};
// taking the average: double average = 0; for(int i=0; i<scores.length; i++) { average += scores[i]; } average /= scores.length; System.out.println("The average score is: "+ average); } {
Close, I have cleaned up the code to make it a bit nicer looking. You don't need to worry about the names array or the grades array, each of those will have a single value.
Here it is:
CODE
public static void main(String[] args){ char grade; Scanner input = new Scanner(System.in);
// Get the names of each student System.out.println("Enter student's name: "); String student = input.nextLine();
// Get student scores System.out.println("Insert 4 test scores:"); double[] scores ={input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble()};
// taking the average: double average = 0; for (int i = 0; i < scores.length; i++){ average += scores[i]; } average /= scores.length; System.out.println("The average score is: " + average);
if (average >= 90) grade = 'A'; else if (average >= 80) grade = 'B'; else if (average >= 70) grade = 'C'; else if (average >= 60) grade = 'D'; else grade = 'F'; System.out.println(student + " has an " + grade + " in the class."); }
NOTE - This is only the main method (function), not the whole class
Well, I'm able to add five names now, but only one set of scores.
I want to be able to add the (1st) name & (4) test scores, (2nd) name & (4) test scores, etc., and then display the names, grades & averages.
Can anyone help me out with this?
CODE
import java.util.Scanner; // Needed for Scanner class public class GraBook { public static void main(String[] args) {
final int STUDENTS = 5;// Number of students final char LETTERS = 5; // Number of grades final int TESTS = 4; // Number of tests
// Create an array to hold students names. char[] grades = new char[LETTERS]; double[] score1 = new double[TESTS]; double[] score2 = new double[TESTS]; double[] score3 = new double[TESTS]; double[] score4 = new double[TESTS]; char grade;
Scanner input = new Scanner(System.in);
// Get the names of each student System.out.println("Enter student's name: "); String student = input.nextLine(); String[] names ={input.nextLine(), input.nextLine(), input.nextLine(), input.nextLine()};
// Get student scores System.out.println("Insert 4 test scores:"); double[] scores ={input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble()};
// Average 4 test scores: double average = 0; for (int i = 0; i < scores.length; i++) { average += scores[i]; } average /= scores.length;
if (average >= 90) grade = 'A'; else if (average >= 80) grade = 'B'; else if (average >= 70) grade = 'C'; else if (average >= 60) grade = 'D'; else grade = 'F';
System.out.println(student + " has a(n) " + grade + " with an average test score of " + average); } }
I've tried about every loop to enable user to enter 1st Student Name, 4 Test Scores 2nd Student Name, 4 Test Scores ... 5th Student Name, 4 Test Scores, but even without errors, I can only get user to input 1st - 5th Name 1 set of test scores
Does anyone have any suggests? Thanks in advance!
CODE
import java.util.Scanner; // Needed for Scanner class public class GraBook { public static void main(String[] args) {
final int STUDENTS = 5;// Number of students final char LETTERS = 5; // Number of grades final int TESTS = 4; // Number of tests
// Create an array to hold students names. char[] grades = new char[LETTERS]; double[] score1 = new double[TESTS]; double[] score2 = new double[TESTS]; double[] score3 = new double[TESTS]; double[] score4 = new double[TESTS]; char grade;
Scanner input = new Scanner(System.in);
// Get the names of each student for (int i=0; i < names.length; i++) { System.out.println("Enter student's name: " + (i + 1) + ": ");; String[i] = keyboard.nextString();
// Get student scores System.out.println("Insert 4 test scores:"); double[] scores ={input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble()};
// Average 4 test scores: double average = 0; for (int i = 0; i < scores.length; i++) { average += scores[i]; } average /= scores.length;
if (average >= 90) grade = 'A'; else if (average >= 80) grade = 'B'; else if (average >= 70) grade = 'C'; else if (average >= 60) grade = 'D'; else grade = 'F';
System.out.println(student + " has a(n) " + grade + " with an average test score of " + average); } }
Sadly Java doesn't seem to allow you to have multi-dimensional arrays, so we have to make a new class to hold things.
Here is the code I came up with:
Student.java:
CODE
import java.util.Scanner;
public class Student{ public static void main(String[] args){ Scanner input = new Scanner(System.in); Record[] students = {new Record(), new Record(), new Record(), new Record(), new Record()}; for(int x=0; x<5; x++){ if(x>0){ input.nextLine(); } System.out.println("Insert student name:"); students[x].setName(input.nextLine()); System.out.println("Insert 5 scores:"); double[] scores = {input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble(), input.nextDouble()}; students[x].setScores(scores); System.out.println(students[x].getAvg()); }
for(int i=0; i<students.length; i++){ System.out.println("Student entry #"+i+". Name "+students[i].getName()+" Average Test Score "+students[i].getAvg()); } } }
Record.java:
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public class Record{ private String myName; private double[] myScores; public Record(String name, double[] scores){ myName = name; myScores = scores; } public Record(String name){ myName = name; } public Record(double[] scores){ myScores = scores; } public Record(){ myName = ""; } public double getAvg(){ double sum = 0; for(int i=0; i<myScores.length; i++){ sum += myScores[i]; } sum /= myScores.length; return sum; } public String getName(){ return myName; } public void setName(String name){ myName = name; } public void setScores(double[] scores){ myScores = scores; } public void addScore(double score){ myScores[myScores.length] = score; } }
Basicall, the Student class has the main method and creates an array of Records. The records each have an array of test scores, myScores, that can be set.
To declare multi-dimensional arrays in Java, use multiple square brackets [].
[code] double [][] tests = new double [STUDENTS][TESTS]; [\code]
When you prompt for data,save immediately to an array location instead of a variable. Use an outer loop to prompt for the name. After saving a name, use an inner loop to prompt and save the values for test scores into the proper location in your two-dimensional array for storing test scores.
When you finish your outer loop, you will have stored all scores. The next step would be to sum all scores in your two-dimensional array and calculate the average.
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