Referencing the array variables in the Reference class, sorting it using another method, and invoking the sorted values in the case statement

Question

I am trying to call the array variables in the reference class, try to sort them using a user-defined method and call the method onto the case statement that will be invoked if the user chooses a particular number. I wanted to provide the user the option what attribute of a student will be sorted (i.e. name, course...) and show the sorted one dimensional array called in the case statements and invoked through the main method.

Here's the variables in the Reference class:

class RecordReference {
private int idNumber;
private String firstName = "";
private String middleName = "";
private String lastName = "";
private int age;
private String yearLevel;
private String course = "";
private double gwa;

public RecordReference(int i, String f, String m, String l, int a, String y, String c, double g) {
    idNumber = i;
    firstName = f;
    middleName = m;
    lastName = l;
    age = a;
    yearLevel = y;
    course = c;
    gwa = g;
}

public int getIdNumber() {
    return idNumber;
}

public String getFirstName() {
    return firstName;
}

public String getMiddleName() {
    return middleName;
}

public String getLastName() {
    return lastName;
}

public int getAge() {
    return age;
}

public String getYearLevel() {
    return yearLevel;
}

public String getCourse() {
    return course;
}

public double getGwa() {
    return gwa;
}


public void setIdNumber(int idnumber) {
    idNumber = idnumber;
}

public void setFirstName(String fName) {
    firstName = fName;
}

public void setMiddleName(String mName) {
    middleName= mName;
}

public void setLastNameName(String lName) {
    lastName= lName;
}

public void setAge(int a) {
    age = a;
}

public void setYearLevel(String yLevel) {
    yearLevel = yLevel;
}

public void setCourse(String c) {
    course = c;
}

public void setGwa(int gwa) {
    gwa = gwa;
}


public String toString() {
    return String.valueOf(System.out.printf("%-15s%-15s%-15d%-15d%n",
            firstName, course , yearLevel  ,gwa));
}

} // end of class

And I am trying to call it in this sort method, but I don't know how to reference it.

public static void sortFirstNameArray(String[] f){
    for (int i = 0; i < f.length - 1; i++) {
        for (int j = i + 1; j < f.length; j++) {
            if (f[i].compareToIgnoreCase(f[j]) > 0) {
                String temp = f[i];
                f[i] = f[j];
                f[j] = temp;
            }
        }
    }
}

After the sorting is successfully done, I'll call it in a switch case statements that will be invoked once the user chooses a particular number. This part has 5 case statements (Name, Age, Course, General Weighted Average and the option to sort it all - I plan to add more student attributes if this works)

(I don't know if I should store this in another method and call it in the main method or just put it in the main method like that)

public RecordReference Process(RecordReference[] f, RecordReference[] a) {
    // for loop?
    for (int x = 0; x < f.length; x++) {
        switch (choice) {
            case 1:
                System.out.println("Sorted array of first name: ");
                sortFirstNameArray(f[x].getFirstName());
                System.out.printf("%-15s%n", Arrays.toString(f));
                break;

            case 2:
                System.out.println("Sorted array of age: ");
                // invokes the age method
                sortAgeArray(a[x].getAge());
                System.out.printf("%-15s%n", Arrays.toString(a));
                break;
        }
    }
} 

If it is in another method, what param do I include when I call it in the main method? I tried this but it doesn't work, I don't know what to do

    System.out.print("Please choose what student attribute you want to 
   sort :");
    choice = keyboard.nextInt();

    // calling the process method here, but I receive syntax error
    Process(f,a); // Here, I want to pass the sorted values back into the array but I get an error. 

If you can help me out that would be great. Thank you in advance.

I'm just a first year student and I am eager to learn in solving this error.

Answer 1

It's good to see that you have attempted the problem yourself and corrected your question to make it clearer, because of that I am willing to help out.

I have tried to keep the solution to the problem as close to your solution as possible, so that you are able to understand it. There may be better ways of solving this problem but that is not the focus here.

First of all, let's create a class named BubbleSorter that will hold methods for sorting:

public class BubbleSorter
{
  //Explicitly provide an empty constructor for good practice.
  public BubbleSorter(){}

  //Method that accepts a variable of type RecordReference[], sorts the 
  //Array based on the firstName variable within each RecordReference 
  //and returns a sorted RecordReference[].
  public RecordReference[] SortByFirstName(RecordReference[] recordReferencesList)
  {
      for (int i = 0; i < recordReferencesList.length - 1; i++) {

        for (int j = i + 1; j < recordReferencesList.length; j++) {

          if (recordReferencesList[i].getFirstName().compareToIgnoreCase                    
             (recordReferencesList[j].getFirstName()) > 0) {

             RecordReference temp = recordReferencesList[i];
             recordReferencesList[i] = recordReferencesList[j];
             recordReferencesList[j] = temp;
            
          }
        }
      }

      return recordReferencesList;
  }
}

That gives us a class that we can instantiate, where methods can be added to be used for sorting. I have added one of those methods which takes a RecordReference[] as a parameter and sorts the RecordReference[] based on the firstName class variable within each RecordReference. You will need to add more of your own methods for sorting other class variables.

Now for the main class:

class Main {
  public static void main(String[] args) {

    //Get a mock array from the GetMockArray() function.
    RecordReference[] refArray = GetMockArray();

    //Instantiate an instance of BubbleSorter.
    BubbleSorter sorter = new BubbleSorter();

    //Invoke the SortByFirstName method contained within the BubbleSorter 
    //and store the sorted array in a variable of type RecordReference[] named 
    //sortedResult.
    RecordReference[] sortedResult = sorter.SortByFirstName(refArray);

    //Print out the results in the sorted array to check if they are in the correct 
    //order.
    //This for loop is not required and is just so that we can see within the 
    //console what order the objects in the sortedResult are in.
    for(int i = 0; i < sortedResult.length; i++)
    {
      System.out.println(sortedResult[i].getFirstName());
    }
  }

  public static RecordReference[] GetMockArray()
  {
    //Instantiate a few RecordReferences with a different parameter for 
    //the firstName in each reference.
    RecordReference ref1 = new RecordReference(0, "Ada", "Test", "Test", 22, "First", 
                                               "Computer Science", 1.0f);

    RecordReference ref2 = new RecordReference(0, "Bob", "Test", "Test", 22, "First", 
                                               "Computer Science", 1.0f);

    RecordReference ref3 = new RecordReference(0, "David", "Test", "Test", 22, 
                                               "First", "Computer Science", 1.0f);

    //Create a variable of type RecordReference[] and add the RecordReferences 
    //Instantiated above in the wrong order alphabetically (Based on their firstName) 
    //class variables.
    RecordReference[] refArray = {
      ref2, ref3, ref1
    };

    return refArray;
  }
}

In the main class I have provided verbose comments to explain exactly what is happening. One thing I would like to point out is that I have added a method named GetMockArray(). This is just in place to provide a RecordReference[] for testing and you probably want to do that somewhere else of your choosing.

If anything is not clear or you need some more assistance then just comment on this answer and I will try to help you further.

Thanks.