Develop Reference

Why am I not getting any values back?

When running the below method, I do not get anything back. Always getting terminated without any results. Could someone tell me why I am not getting any results back?
I hava adjusted according to the comments but havent worked. I have add the main method below;
public class ModuleGrader {
final int examID = 123;
String excellent =null;
String good=null;
String satisfactory=null;
String compensatableFail=null;
String outrightFail=null;
int grade;
public String gradeModule(int mark) {
String result = null;
if (mark>=70 && mark<=100)
{
result = excellent;
System.out.println(" ");
}
else if (mark>=60 && mark<=69)
{
result = good;
}
else if (mark>=50 && mark<=59)
{
result = satisfactory;
}
else if (mark>=40 && mark<=49)
{
result = compensatableFail;
}
else if (mark>=0 && mark<=39) {
result = outrightFail;
}
else {
System.out.println("Invalid entery, please insert an number between 100-0");
}
return result;
}
So I have add my invoking main method;
the method to call maybe the problem?
public static void main(String[] args) {
ModuleGrader mg=new ModuleGrader();
mg.gradeModule(100);
mg.gradeModule(66);}

You have assigned no values to String excellent;, String good;, so it fails because those values have not been initialized to anything when you call them.
How would you know that it is not working? You have no output of the final result to the console. I added System.out.println() to correct that.
You can't reference something which is not static from something which is static. Change public class ModuleGrader to public static class ModuleGrader.
Final Working Code
public class Main {
public static void main(String[] args) {
ModuleGrader mg=new ModuleGrader();
System.out.println(mg.gradeModule(100));
System.out.println(mg.gradeModule(66));
}
public static class ModuleGrader {
final int examID = 123;
String excellent = null;
String good = null;
String satisfactory = null;
String compensatableFail = null;
String outrightFail = null;
int grade;
public String gradeModule(int mark) {
String result = null;
if (mark >= 70 && mark <= 100) {
result = excellent;
System.out.println(" ");
} else if (mark >= 60 && mark <= 69) {
result = good;
} else if (mark >= 50 && mark <= 59) {
result = satisfactory;
} else if (mark >= 40 && mark <= 49) {
result = compensatableFail;
} else if (mark >= 0 && mark <= 39) {
result = outrightFail;
} else {
System.out.println("Invalid entery, please insert an number between 100-0");
}
return result;
}
}
}
You need to put quotes around the strings you want to assign.
result = excellent; should be result = "excellent"; and soforth for all your assignments to return

public class ModuleGrader {
final int examID = 123;
//String excellent=null;
//String good=null;
//String satisfactory=null;
//String compensatableFail=null;
//String outrightFail=null;
int grade;
public String gradeModule(int mark) {
String result = null;
if (mark>=70 && mark<=100)
{
result = "excellent";
System.out.println(" ");
}
else if (mark>=60 && mark<=69)
{
result = "good";
}
else if (mark>=50 && mark<=59)
{
result = "satisfactory";
}
else if (mark>=40 && mark<=49)
{
result = "compensatableFail";
}
else if (mark>=0 && mark<=39) {
result = "outrightFail";
}
else {
System.out.println("Invalid entery, please insert an number between 100-0");
}
return result;
}

junit.framework.AssertionFailedError - Incomplete Stack Trace Given

Full Disclosure: This was an assignment, it has been marked already, but I want to understand why I'm getting this error.
I'm having some issues understanding why junit.framework.AssertionFailedError is being thrown. Normally when errors occur I could at least look at the stack trace and see what is happening. In this case, the output console shows this:
Testcase: testIsCorrectMCQ(mr_3.myTester): FAILED
null
junit.framework.AssertionFailedError
at mr_3.MyTester.testIsCorrectMCQ(Assign03Tester.java:207)
testIsCorrectMCQ(mr_3.MyTester): FAILED
In the test result tab in NetBeans, copying the stack trace gives me:
junit.framework.AssertionFailedError
at mr_3.myTester.testIsCorrectMCQ(myTester.java:207)
In the tester file, I have this:
#Test
public void testIsCorrectMCQ() {
System.out.println("isCorrect of MCQ");
MCQuestion instance = new MCQuestion(1,"Capital city of Canada is", 'A',
"Ottawa", "Vancouver", "New York", "Toronto");
assertFalse(instance.isCorrect("B"));
assertTrue(instance.isCorrect("A")); // line 207
}
My isCorrect method is this:
#Override
public boolean isCorrect(Object guess) {
if (guess == null)
return false;
if (guess instanceof String) {
String userGuess = (String)guess;
return (userGuess.charAt(0) == this.getAnswer());
}
if (guess instanceof Character) {
Character userGuess = (Character)guess;
return (userGuess == this.getAnswer());
}
else return false;
}
Any help in understanding what is happening is greatly appreciated.
Edit 1 : My MCQuestion source code
public class MCQuestion extends Question {
private char answer;
private String[] options;
public MCQuestion() {
super();
questionType = QuestionType.MULTIPLE_CHOICE;
}
public MCQuestion(int id, String text, char answer, String... options) {
super(id, text);
setOptions(options);
setAnswer(answer);
questionType = QuestionType.MULTIPLE_CHOICE;
}
public String[] getOptions() {
String[] getOptions = new String[this.options.length];
System.arraycopy(this.options, 0, getOptions, 0, this.options.length);
return getOptions;
}
public void setOptions(String... options) {
if (options.length > 0) {
this.options = new String[options.length];
for (int i = 0; i < options.length; i++) {
if (options[i].isEmpty())
throw new IllegalArgumentException("You have nothing in this option");
else
this.options[i] = options[i];
}
}
else throw new IllegalArgumentException("You have no options set");
}
public char getAnswer() {
return this.answer;
}
public void setAnswer(char ans) {
ans = Character.toLowerCase(ans);
int index = ans - 97;
if (Character.isLetter(ans) && index >= 0 && index < this.options.length)
this.answer = ans;
else throw new IllegalArgumentException(ans + " is not a valid answer option");
}
#Override
public boolean isCorrect(Object guess) {
if (guess == null)
return false;
if (guess instanceof String) {
String userGuess = (String)guess;
return (userGuess.charAt(0) == this.getAnswer());
}
if (guess instanceof Character) {
Character userGuess = (Character)guess;
return (userGuess == this.getAnswer());
}
else return false;
}
#Override
public String toString() {
String option = "";
if (this.options.length == 0)
option = "No options added, yet!";
else {
char index = 'a';
for (String e: options)
option += index + ") " + e + "\n";
}
return (super.toString() + "\n" + option);
}
}

You execute ans = Character.toLowerCase(ans); for whatever reason in your setAnswer() method before saving it in this.answer. This means that (userGuess.charAt(0) == this.getAnswer()) will return false when you provide the answer in upper case, but compare it with the stored lower case character.
Depending on if you want case insensitive answers or not, you should add or remove the Character.toLowerCase() call to your isCorrect() method as well.

How Do I Process objects in my custom linked list?

I successfully made a linked list, but now I am having trouble processing it. What methods do I need to add to my FoodList class to be able to process my objects? For example, I need to have the user be able to choose to manually add food objects together so I can print a meal. Also, I can't use any collections classes from the java API. It all must be custom.
public static void main(String[] args) {
FoodList list = new FoodList();
boolean keepGoing = true;
int scanResultInt;
try
{
//I/O stream
FileReader fr = new FileReader("foodlist.txt");
BufferedReader br = new BufferedReader(fr);
Scanner scan = new Scanner(br);
Food hold = new Food();
while(scan.hasNext()){
list.add(hold = new Food());
String str = scan.next();
//str = scan.next();
hold.setName(str);
str = scan.next();
hold.setGroup(str);
int cal = scan.nextInt();
hold.setNumCal(cal);
double percent = scan.nextDouble();
hold.setPercentDV(percent);
list.add(hold);
}
//System.out.println("" + list.toString());
br.close(); //close I/O stream
}
catch(IOException e){
System.err.println("I/O EXCEPTION: " + e.getMessage());
}
Scanner scan2 = new Scanner(System.in);
do {
System.out.println("---------------------------------------------------------");
System.out.println(" Welcome to the Parkland Meal Selector" );
System.out.println("---------------------------------------------------------");
System.out.println("Enter the number of the menu option you would like to select:");
System.out.println(" 1) List food database");
System.out.println(" 2) Create meal by manual selection");
System.out.println(" 3) Create meal by random selection");
System.out.println(" 4) Remove foods high in calories");
System.out.println(" 5) Exit");
scanResultInt = scan2.nextInt();
switch(scanResultInt) {
case 1: {
System.out.println("" + list.toString());
break;
}
case 2: {
System.out.println("Create-A-Meal Menu\n");
System.out.println("Enter the name of a food you would like to add:\n");
String foodWanted = scan2.next();
/*while( != null){
if(foodWanted.equals());
}*/
/*Food tmp;
for(tmp = head; tmp != null; tmp = tmp.next)
{
result += tmp.f;
}
return result;*/
}
case 3: {
System.out.println("Create meal by random selection: \n");
break;
}
case 4: {
System.out.println("Remove Food High In Calories: \n");
break;
}
case 5: {
keepGoing = false;
break;
}
}
}
while(keepGoing);
}
Here is my Linked List:
public class FoodList {
// Class fields
private FoodNode head;
private int listCount;
// Private inner class
private class FoodNode
{
public Food f;
public FoodNode next;
public FoodNode(Food f)
{
this.f = f;
this.next = null;
}
}
// Constructor for LinkedList
public FoodList()
{
// Initialize start of the list
head = null;
listCount = 0;
}
// Add method (adds a reservation to the linked list)
public void add(Food f)
{
// Create a new ReservationNode
FoodNode node = new FoodNode(f);
// If this is the first node
if( head == null )
head = node;
else
{
FoodNode tmp = head;
while(tmp.next != null)
tmp = tmp.next;
tmp.next = node;
}
listCount++
}
/*public boolean hasThatFood(String food){
boolean haveThat = false;
FoodNode tmp;
for(tmp = head; tmp != null; tmp = tmp.next)
{
if (food == f.getName());
haveThat = true;
}
return haveThat;
}*/
/*public boolean hasNext(){
boolean hasNext = false;
if(head != null) {
hasNext = true;
return hasNext;
}
}*/
#Override
public String toString() {
String result = "My Foods:" + '\n';
// Loop through all the reservation nodes
FoodNode tmp;
for(tmp = head; tmp != null; tmp = tmp.next)
{
result += tmp.f;
}
return result;
}
}
And my Food class
public class Food {
private String name;
private String group;
private int numCal;
private double percentDV;
public Food() {//String name, String group, int numCal, double percentDV
/*this.name = name;
this.group = group;
this.numCal = numCal;
this.percentDV = percentDV;*/
name = "";
group = "";
numCal = 0;
percentDV = 0.0;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getGroup() {
return group;
}
public void setGroup(String group) {
this.group = group;
}
public int getNumCal() {
return numCal;
}
public void setNumCal(int numCal) {
this.numCal = numCal;
}
public double getPercentDV() {
return percentDV;
}
public void setPercentDV(double percentDV) {
this.percentDV = percentDV;
}
#Override
public String toString() {
return "Food{" +
"name: '" + name + '\'' +
", Food Group: '" + group + '\'' +
", Calories: " + numCal +
", Daily Percent: " + percentDV +
'}';
}
}
I know this is spaghetti code, but this is my last resort. Any help would be appriciated!

To operate on the objects you have to write your custom Iterator. I guess here is nothing criminal to open LinkedList source and look how it works.

Something like this, You can find many resource online,
https://crunchify.com/how-to-implement-a-linkedlist-class-from-scratch-in-java/
Here is one.
public Object getElement(int index)
{
if (index < 0)
return null;
Node Current = null;
if (head != null) {
Current = head.getNext();
for (int i = 0; i < index; i++) {
if (Current.getNext() == null)
return null;
Current = Current.getNext();
}
return Current.getData();
}
return Current;
}

You have implemented some complicated classes. Inner logic of its is not very clear like your issue. So almost any answer will not cover your needs.
If I would you I would try recommend the logic using java core tools (without implementing classes, that implemented in best way LinkedList, ArrayList...). Logic should be converted into some structural solution. For example:
enter point creates and calls your stream service to handle provided input stream;
stream handler should manipulate builder;
builder result have to be collected into composite;
and so on...
If you provide your logic in more structural way you would ask more clear question pointing the issue. Also I believe your question will disappear after this preparation.
Also I would recommend you to get familiar with next GoF patterns: builder, factory method, composite, strategy.

Java calling method and trapping return

I'm having a problem calling a method and then trapping its return.
I need it to update the result so the next time round the loop it will see it and return a different message.
public class Patient {
private char patientStatus;
public boolean admit() {
if (patientStatus != 'S')
return false;
else
patientStatus = 'A';
return true;
}
This section is in the main() method
do {
Patient temp = null;
System.out.print("Enter selection: ");
menuSelect = sc.nextLine();
// validation
if (menuSelect.length() != 1) {
System.out.println("You must enter a single character");
} else {
menuAnswer = menuSelect.charAt(0);
switch (menuAnswer) {
case 'A':
case 'a':
// patient number
System.out.print("Enter patient number: ");
patNumber = sc.nextLine();
// search for patient number
for (int i = 0; i < pat.length && temp == null; i++) {
if (pat[i].getPatientNo().equals(patNumber)) {
temp = pat[i];
}
}
if (temp == null) {
System.out.println("Patient not found");
} else {
System.out.println("Patient " + patNumber + " Found");
boolean patStatus = temp.admit();
if (patStatus == false) {
System.out.println("Admitted");
} else if (patStatus == true) {
System.out.println("Already admitted");
}
}
}
}
} while (menuAnswer != 'x' && menuAnswer != 'X');
System.out.println("Exiting menu");
I don't know how to update the patStatus so the next time in the menu if you select 'A' and the same patient number it returns "Already admitted".
Let me know if there's enough code to understand what's happening.

Your Patient has the atribute for patientStatus but its value is never saved. Your admit() method needs to set the value for it.
Currently, your code only returns the value but does not save it.
Try this:
public class Patient {
private char patientStatus;
/** "Getter" method for patientStatus
*/
public char getPatientStatus(){
return patientStatus;
}
/** "Admits" the new patient, changing its patientStatus
* #return "true" if patient is admitted; "false" if patient was already admitted.
*/
public boolean admit() {
if (patientStatus != 'A')
patientStatus = 'A'; //set the value to Admitted
return true;
else
return false;
}
}
Then, in your loop, test the value for the admit() call:
if (temp == null) {
System.out.println("Patient not found");
} else {
System.out.println("Patient " + patNumber + " Found");
boolean admitted = temp.admit(); // try to admit the patient
if (admitted) {
System.out.println("Admitted");
} else { //You don't need another if here
System.out.println("Already admitted");
}
}
Since admitted is of type boolean, you don't need to use the == operator, as the if statement uses a boolean value as argument.
You don't need a second if statement after the else either, since boolean can only have two values, if it is not true, then it can only be false

/* You have to re-factor the code on these lines.
Maintain Patients class which holds admitted patients.*/
public class Patients{
private ConcurrentHashMap<Integer, Patient> allPatients = new ConcurrentHashMap();
private HashSet<Integer) admittedPatients = new HashSet();
public Patients(){
}
public void add(Patient p){
allPatients.put(p.getPatientId(),p);
}
public Patient removePatient(int patientId){
dischargePatients.remove(patientId);
return allPatients.remove(patientId);
}
public Patient getPatient(int patientId){
return allPatients.get(patientId);
}
public void admitPatient(int patientId){
admittedPatients.add(patientId);
}
public boolean dischargePatient(int patientId){
return admittedPatients.remove(patientId);
}
public boolean isAdmittedPatient(int patientId){
return admittedPatients.contains(patentId);
}
}
From `Patient.java` class, you can admit & discharge patient.
If getPatient() is null implies patient is not present in list.
Once he is present, isAdmittedPatient returns whether
he is admitted or not.

illegal start of expression public boolean setTuitionFees;(double fees);{ [closed]

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Closed 10 years ago.
I'm trying to create a method so I can set the "tuitionFees" and "scholarships" as a double for the profile of the user of the program. I'm unsure if I'm even setting this up right.
import java.util.Scanner;
/**
StudentInvoice.java
Defines StudentInvoice objects
#author: Evan Fravert
*/
public class StudentInvoice {
// declare instance variables here
// constructor
// methods
// toString method (for String output)
private String studentName;
private String studentNumber;
private double tuitionFees;
private double scholarships;
public String toString() {
String output = "Name: " + studentName + "\n";
output += "Student ID Number: " + studentNumber + "\n";
output += "Tuition & Fees: " + tuitionFees + "\n";
output += "Scholarship: " + scholarships + "\n";
return output;
}
public StudentInvoice(String name, String number, double fees, double scholarship){
studentName = name;
studentNumber = number;
tuitionFees = fees;
scholarships = scholarship;
}
public boolean setStudentName(String name){
if(name.length() == 0)
{
return false;
}
else
{
studentName = name;
return true;
}
}
public boolean setStudentNumber(String number){
if(number.length() == 0)
{
return false;
}
else
{
studentNumber = number;
return true;
}
public boolean setTuitionFees(double fees){
if(fees < 0.0) {
return false;
}
else {
tuitionFees = fees;
return true;
}
}
public boolean setScholarships (double scholarship){
if(scholarship < 0.0) {
return false;
}
else {
Scholarships = scholarship;
return true;
}
}
}
}
My class with the interactions:
public class StudentInvoiceApp {
public static void main (String[] args) {
StudentInvoice Evan = new StudentInvoice("Evan Fravert");
Evan.setName("Evan Fravert");
Evan.setNumber(01234);
Evan.setTuitionFees(0.00);
Evan.setScholarship(0.00);
System.out.print(Evan);
}
}

Upon trying to edit your post, I discovered you had a missing brace after setStudentNumber. The corrected code with proper formatting is below. In any programming language, formatting your code is important to understanding its meaning. People write entire books on how to format code, and for good reason. With good formatting, you likely would have noticed the missing brace.
Searching for "How to format Java code" yields several useful conventions, including documents from Oracle about how they format their Java code. When in doubt, most IDE's provide shortcuts to format code as well. In Eclipse, it's Ctrl+Shift+F, and in NetBeans, it's Alt+Shift+F.
import java.util.Scanner;
/**
* StudentInvoice.java Defines StudentInvoice objects
*
* #author: Evan Fravert
*/
public class StudentInvoice {
// declare instance variables here
// constructor
// methods
// toString method (for String output)
private String studentName;
private String studentNumber;
private double tuitionFees;
private double scholarships;
public String toString() {
String output = "Name: " + studentName + "\n";
output += "Student ID Number: " + studentNumber + "\n";
output += "Tuition & Fees: " + tuitionFees + "\n";
output += "Scholarship: " + scholarships + "\n";
return output;
}
public StudentInvoice(String name, String number, double fees,
double scholarship) {
studentName = name;
studentNumber = number;
tuitionFees = fees;
scholarships = scholarship;
}
public boolean setStudentName(String name) {
if (name.length() == 0) {
return false;
} else {
studentName = name;
return true;
}
}
public boolean setStudentNumber(String number) {
if (number.length() == 0) {
return false;
} else {
studentNumber = number;
return true;
}
}
public boolean setTuitionFees(double fees) {
if (fees < 0.0) {
return false;
} else {
tuitionFees = fees;
return true;
}
}
public boolean setScholarships(double scholarship) {
if (scholarship < 0.0) {
return false;
} else {
scholarships = scholarship;
return true;
}
}
}

change your setStudentNumber method to this
public boolean setStudentNumber(String number){
if(number.length() == 0)
{
return false;
}
else
{
studentNumber = number;
return true;
}
}
you were missing an closing brace for else