So I'm making a program for a car dealership as my final project for my class. At this time I'd say I'm about 75% done, but I am having trouble figuring out how to update the users input in an array list. So each array list slot contains the year, make, model, color, and mileage of a car. I can add a new car, I can remove a car, and I can quit my program. I have tried many things, I've read many papers, blogs, forums, and my book for class, but its always updating with the programmers input.
package carDealer;
import java.util.ArrayList;
import java.util.Scanner;
public class VehicleInformation {
public static void main(String [] args) {
Scanner scnr = new Scanner(System.in);
ArrayList<VehicleInventory> car = new ArrayList<VehicleInventory>();
String userInput = "-";
while (!userInput.equals("q")) {
System.out.println("Commands: 'a' to add, 'd' to delete, 'e' to edit, 'q' to quit");
userInput = scnr.next();
if (userInput.equals("a")) {
System.out.println("Year: ");
int year = scnr.nextInt();
System.out.println("Make: ");
String make = scnr.next();
System.out.println("Model: ");
String model = scnr.next();
System.out.println("Color: ");
String color = scnr.next();
System.out.println("Mileage: ");
int mileage = scnr.nextInt();
VehicleInventory userCar = new VehicleInventory();
userCar.setMake(make);
userCar.setModel(model);
userCar.setYear(year);
userCar.setColor(color);
userCar.setMileage(mileage);
userCar.print();
addCar(car, userCar);
}
if (userInput.equals("d")) {
for (int i = 0; i < car.size(); ++i) {
System.out.print((i + 1) + " ");
car.get(i).print();
}
System.out.println("List number: ");
int userNum = scnr.nextInt();
car.remove(userNum - 1);
System.out.println("count: " + car.size());
}
if (userInput.equals("e")) {
for (int i = 0; i < car.size(); ++i) {
System.out.print((i + 1) + " ");
car.get(i).print();
}
System.out.println("List number: ");
int userNum = scnr.nextInt();
car.get(userNum - 1);
You can just do a loop to look up for the car model the user wants to update (it can be any other attribute), and once found update it's value with the desired one:
String vehicleToLookUp = "golf"; // This will be received by user input
String vehicleNewName = "golf gti"; // This will be received by user input
for( int i = 0; i < car.size(); i++){
if(vehicleToLookUp.getModel().equals(car.get(i)){
car.get(i).setSomeAttribute(...); // Set the desired attribute here
}
}
Or if you want to substitute the whole object...
String vehicleToLookUp = "golf"; // This will be received by user input
VehicleInventory newVehicle = new VehicleInventory(); // You will set the attributes by user input
for( int i = 0; i < car.size(); i++){
if(vehicleToLookUp.getModel().equals(car.get(i)){
car.set(i, newVehicle ); // Create your object and pass it here
}
}
Also, instead of all those if, you could use if/else if or even a switch/case for better performance/readability (think that even if your logic is true for first if, it will check for all the other if you created, wasting time and processing power.
Related
I wanna ask if this is possible. So I have this program will enter a for loop to get the user input on number of subjects. Then after he will enter the subjects listed in the array as his guide. My goal is that I want to check his subjects if it is really inside the array that I made. I made a program but I don't know where to put the part that the program will check the contents.
My goal:
Enter the corresponding code for the subjects you have chosen: user will input 8
Enter the number of subjects you wish to enroll: be able to type the whole subject name like (MATH6100) Calculus 1
then the program will check if the subjects entered are part of the elements inside the array
UPDATE:
I have made another but the problem is that I don't know where to put the code fragment wherein it will check the contents of the user input for list of subjects he wish to enroll.
Here is the code:
private static void check(String[] arr, String toCheckValue){
boolean test=Arrays.asList(arr).contains(toCheckValue);
System.out.println("Is/Are " + toCheckValue + " present in the array: " + test);
}
public static void main(String[] args){
String arr[]={"(MATH6100) Calculus 1", "(ITE6101) Computer Fundamentals", "(ITE6102) Computer Programming 1", "(GE6100) Understanding the Self", "(GE6106) Purposive Comunication 1", "(ETHNS6101) Euthenics 1", "(PHYED6101) Physical Fitness", "(NSTP6101) National Service Training Program 1"};
Scanner input1=new Scanner(System.in);
System.out.print("\nEnter the number of subjects you wish to enroll: ");
int number_subjects1=input1.nextInt();
String []subjects1=new String[number_subjects1];
//else statement when user exceeds the number of possible number of subjects
if(number_subjects1<=8){
for(int counter=0; counter<number_subjects1; counter++){
System.out.println("Enter the corresponding code for the subjects you have chosen (EX. MATH6100): " + (counter+1));
subjects1[counter]=input1.next();
}
String toCheckValue=subjects1[0];
System.out.println("Array: " +Arrays.toString(arr));
check(arr, toCheckValue);
System.out.println("\nPlease check if these are your preferred subjects:");
for(int counter=0; counter<number_subjects1; counter++){
System.out.println(subjects1[counter]);
}System.out.println("********************************** \n" + "\tNothing Follows");
System.out.print("\nIf you have enter some errors please press Y and refresh the form (Y/N): ");
Scanner character=new Scanner(System.in);
String answer_1subjectserrors=character.nextLine();
System.out.println(answer_1subjectserrors + "Based on your answer, you need to refresh thae page and try again.");
}
}
}
I believe the issue is that you are checking your class course codes against an array which contains both the class code AND the class description.
You ask the user to enter the class code but then you use that code to check for its existence in an array containing both the code & description. The contains in List (collections) is not the same as the contains in String.
I have slightly modified your code so you may get the desired result.
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class SOQuestion {
private static void check(String[] arr, String toCheckValue){
List courses = Arrays.asList(arr);
boolean test=courses.contains(toCheckValue);;
System.out.println("Is/Are " + toCheckValue + " present in the array: " + test);
}
public static void main(String[] args) {
String class_codes_and_descriptions[] = { "(MATH6100) Calculus 1", "(ITE6101) Computer Fundamentals", "(ITE6102) Computer Programming 1",
"(GE6100) Understanding the Self", "(GE6106) Purposive Comunication 1", "(ETHNS6101) Euthenics 1",
"(PHYED6101) Physical Fitness", "(NSTP6101) National Service Training Program 1" };
String class_codes[] = { "MATH6100", "ITE6101", "ITE6102","GE6100", "GE6106", "ETHNS6101","PHYED6101", "NSTP6101" };
Scanner input1 = new Scanner(System.in);
System.out.print("\nEnter the number of subjects you wish to enroll: ");
int number_subjects1 = input1.nextInt();
String[] subjects1 = new String[number_subjects1];
// else statement when user exceeds the number of possible number of subjects
if (number_subjects1 <= 8) {
for (int counter = 0; counter < number_subjects1; counter++) {
System.out.println("Enter the corresponding code for the subjects you have chosen (EX. MATH6100): "
+ (counter + 1));
subjects1[counter] = input1.next();
}
String toCheckValue = subjects1[0];
System.out.println("Array: " + Arrays.toString(class_codes_and_descriptions));
check(class_codes, toCheckValue);
System.out.println("\nPlease check if these are your preferred subjects:");
for (int counter = 0; counter < number_subjects1; counter++) {
System.out.println(subjects1[counter]);
}
System.out.println("********************************** \n" + "\tNothing Follows");
System.out.print("\nIf you have enter some errors please press Y and refresh the form (Y/N): ");
Scanner character = new Scanner(System.in);
String answer_1subjectserrors = character.nextLine();
System.out.println(
answer_1subjectserrors + "Based on your answer, you need to refresh the page and try again.");
}
}
}
When you are debugging always try to break down the statements into steps so you know where the error is. For example instead of boolean test=Arrays.asList(arr).contains(toCheckValue);
break it down to two steps like this :
List courses = Arrays.asList(arr);
boolean test=courses.contains(toCheckValue);
That way you will have an easier time checking for issues.
Second request is to always look at the API. Skim over the API to look at the method that you are using to understand it better.
For example if you are using contains method of List then look up the API here:
https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/util/List.html#contains(java.lang.Object)
Of course since this is Oracle's Java the explanation is imprecise & not straightforward but it is usually helpful.
I would recommend using a different data structure than plain arrays. Since you are already using List why not use another collections data structure like HashMap?
The original poster may want to look at a slightly refactored and cleaned up version of the code & try to figure out how to check for all courses since that is his next question. I believe that should become obvious with a more refactored code:
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class SOQuestion {
public static String class_codes_and_descriptions[] = { "(MATH6100) Calculus 1", "(ITE6101) Computer Fundamentals", "(ITE6102) Computer Programming 1",
"(GE6100) Understanding the Self", "(GE6106) Purposive Comunication 1", "(ETHNS6101) Euthenics 1",
"(PHYED6101) Physical Fitness", "(NSTP6101) National Service Training Program 1" };
public static String class_codes[] = { "MATH6100", "ITE6101", "ITE6102","GE6100", "GE6106", "ETHNS6101","PHYED6101", "NSTP6101" };
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int desired_number_of_subjects = input_desired_number_of_subjects(input);
String[] desired_subjects = enter_subjects(desired_number_of_subjects, input);
String toCheckValue = desired_subjects[0];
System.out.println("Array: " + Arrays.toString(class_codes_and_descriptions));
check(class_codes, toCheckValue);
pls_confirm_desired_subjects(desired_number_of_subjects, desired_subjects);
System.out.println("********************************** \n" + "\tNothing Follows");
System.out.print("\nIf you have enter some errors please press Y and refresh the form (Y/N): ");
Scanner character = new Scanner(System.in);
String answer_1subjectserrors = character.nextLine();
System.out.println(
answer_1subjectserrors + "Based on your answer, you need to refresh the page and try again.");
}
private static int input_desired_number_of_subjects(Scanner input) {
System.out.print("\nEnter the number of subjects you wish to enroll: ");
int take_number_of_subjects = input.nextInt();
// TODO: else statement when user exceeds the number of possible number of subjects
return take_number_of_subjects;
}
private static String[] enter_subjects(int desired_subjects_count , Scanner input_desired_subjects) {
String[] subjects_totake = new String[desired_subjects_count];
if (desired_subjects_count <= 8) {
for (int counter = 0; counter < desired_subjects_count; counter++) {
System.out.println("Enter the corresponding code for the subjects you have chosen (EX. MATH6100): "
+ (counter + 1));
subjects_totake[counter] = input_desired_subjects.next();
}
}
return subjects_totake;
}
private static void check(String[] arr, String toCheckValue){
List courses = Arrays.asList(arr);
boolean test=courses.contains(toCheckValue);
System.out.println("Is/Are " + toCheckValue + " present in the array: " + test);
}
private static void pls_confirm_desired_subjects(int take_number_of_subjects, String[] take_subjects) {
System.out.println("\nPlease check if these are your preferred subjects:");
for (int counter = 0; counter < take_number_of_subjects; counter++) {
System.out.println(take_subjects[counter]);
}
}
}
I will shortly edit the above but a hint is : you can use a for loop to go over the entered desired_subjects array and do a check on each one of the subjects, perhaps?
The following checks for all the courses (though this is not how I would check the courses)
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class SOQuestion {
public static String class_codes_and_descriptions[] = { "(MATH6100) Calculus 1", "(ITE6101) Computer Fundamentals", "(ITE6102) Computer Programming 1",
"(GE6100) Understanding the Self", "(GE6106) Purposive Comunication 1", "(ETHNS6101) Euthenics 1",
"(PHYED6101) Physical Fitness", "(NSTP6101) National Service Training Program 1" };
public static String class_codes[] = { "MATH6100", "ITE6101", "ITE6102","GE6100", "GE6106", "ETHNS6101","PHYED6101", "NSTP6101" };
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int desired_number_of_subjects = input_desired_number_of_subjects(input);
String[] desired_subjects = enter_subjects(desired_number_of_subjects, input);
check_all_desired_subjects(desired_subjects);
pls_confirm_desired_subjects(desired_number_of_subjects, desired_subjects);
System.out.println("********************************** \n" + "\tNothing Follows");
System.out.print("\nIf you have enter some errors please press Y and refresh the form (Y/N): ");
Scanner character = new Scanner(System.in);
String answer_1subjectserrors = character.nextLine();
System.out.println(
answer_1subjectserrors + "Based on your answer, you need to refresh the page and try again.");
}
private static int input_desired_number_of_subjects(Scanner input) {
System.out.print("\nEnter the number of subjects you wish to enroll: ");
int take_number_of_subjects = input.nextInt();
// TODO: else statement when user exceeds the number of possible number of subjects
return take_number_of_subjects;
}
private static String[] enter_subjects(int desired_subjects_count , Scanner input_desired_subjects) {
String[] subjects_totake = new String[desired_subjects_count];
if (desired_subjects_count <= 8) {
for (int counter = 0; counter < desired_subjects_count; counter++) {
System.out.println("Enter the corresponding code for the subjects you have chosen (EX. MATH6100): "
+ (counter + 1));
subjects_totake[counter] = input_desired_subjects.next();
}
}
return subjects_totake;
}
private static void check_all_desired_subjects(String[] desired_subjects) {
System.out.println("Array: " + Arrays.toString(class_codes_and_descriptions));
for (String subject_code_to_check:desired_subjects ) {
check(class_codes, subject_code_to_check);
}
}
private static void check(String[] arr, String toCheckValue){
List courses = Arrays.asList(arr);
boolean test=courses.contains(toCheckValue);
System.out.println("Is/Are " + toCheckValue + " present in the array: " + test);
}
private static void pls_confirm_desired_subjects(int take_number_of_subjects, String[] take_subjects) {
System.out.println("\nPlease check if these are your preferred subjects:");
for (int counter = 0; counter < take_number_of_subjects; counter++) {
System.out.println(take_subjects[counter]);
}
}
}
I am trying to create a program that generates plane tickets and after that it asks the user if they want to see the passenger list.
What I am struggling with is that after every user that has input their details, they must get added to the passenger list.
So if User1 enters his details and must get asked if they want to see the passenger list (so far there will be only one record under the passenger list), then wen User2 enters his details it must ask the user if they want to see the passenger list and the User2 details must get added to the passenger list (so we will have 2 records under the passenger list) and so on..
Please assist with that.
public class Question12 {
public static void main(String[] args) {
double random = Math.random()* 69 + 1;
String q;
Scanner in = new Scanner(System.in);
String[][] PlaneTicket = new String[3][3];
for (int row = 0; row < 67; row++) {
System.out.print("Enter name:");
PlaneTicket[row][0] = in.next();
System.out.print("Enter surname: ");
PlaneTicket[row][1] = in.next();
System.out.print("Enter a ID: ");
PlaneTicket[row][2] = in.next();
System.out.println("************Airport**********");
System.out.println("Seat number: " + Math.round(random));
System.out.println("Name: " + PlaneTicket[row][0]);
System.out.println("Surname: " + PlaneTicket[row][1]);
System.out.println("ID: " + PlaneTicket[row][2]);
System.out.println("*****************************");
System.out.println("Do you want to view the passanger list: " + "(Yes/No)");
q = in.next();
if ("Yes".equals(q)) {
System.out.println("Name Surname ID Seat Number");
System.out.println("----------------------------------------");
System.out.println(PlaneTicket[row][0]+" "+PlaneTicket[row][1]+" "+PlaneTicket[row][2]+ " "+ Math.round(random));
If you just want to print all the entered values so far, you can do:
System.out.println("Name Surname ID Seat Number");
System.out.println("----------------------------------------");
for (int k = 0; k <= row; k++) {
System.out.println(PlaneTicket[k][0] + " " + PlaneTicket[k][1] + " " + PlaneTicket[k][2] + " " + Math.round(random));
}
Does that answer your question?
Some remarks:
you have to fix the array size (as mentioned in the comments): String[][] PlaneTicket = new String[67][3];
you should create a class PassengerTicket, which would help to make your code more readable (and more object-oriented)
you should redesign your code to utilize methods for the different operations you have (add, print, ...)
your output should be formatted (e.g., using String.format)
you should have a look at Collections, which would make your code more readable and probably easier to maintain, i.e., https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html, https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html
Here is your main method with some fixes, as mentioned please do some redesign (see my remarks):
public static void main(String[] args) {
final int maxPassengers = 67;
double random = Math.random() * 69 + 1;
String q;
Scanner in = new Scanner(System.in);
String[][] PlaneTicket = new String[maxPassengers][4];
for (int row = 0; row < maxPassengers; row++) {
System.out.print("Enter name:");
PlaneTicket[row][0] = in.next();
System.out.print("Enter surname: ");
PlaneTicket[row][1] = in.next();
System.out.print("Enter a ID: ");
PlaneTicket[row][2] = in.next();
// you should keep the SeatNumber
PlaneTicket[row][3] = String.valueOf(Math.round(random));
System.out.println("************Airport**********");
System.out.println("Seat number: " + PlaneTicket[row][3]);
System.out.println("Name: " + PlaneTicket[row][0]);
System.out.println("Surname: " + PlaneTicket[row][1]);
System.out.println("ID: " + PlaneTicket[row][2]);
System.out.println("*****************************");
System.out.println("Do you want to view the passanger list: " + "(Yes/No)");
q = in.next();
if ("Yes".equalsIgnoreCase(q) || "y".equalsIgnoreCase(q)) {
System.out.println("Name Surname ID Seat Number");
System.out.println("----------------------------------------");
for (int k = 0; k <= row; k++) {
System.out.println(PlaneTicket[k][0] + " " + PlaneTicket[k][1] + " " + PlaneTicket[k][2] + " " + PlaneTicket[row][3]);
}
}
}
}
You initialize a two dimensional array PlaneTicket = new String[3][3] and the you run it up to 66.. that clearly gives an IndexOutOfBounds Exception. Best way, avoid magic numbers and put them in a variable such as row or column and then iterate up to it.
Otherwise it looks OK.
Second, be careful with the terms list and array. Do you mean Passengerlist or just an array?
It seems you have it at the bottom, but you miss some brackets. After fixing the indexing, it should work.
You need to create a method displayList(String[][] seats) and call it once each customer types "Yes". This method will have similar loop(s) and display the current list
for (int row = 0; row < 67; row++) { ....}
Hello the StackOverflow community! I am recent Java learner with 1 year of experience only. I was asked to design a software that mimics a school DB, storing all names, class, roll, and other details. When asked to, it would display appropriate messages, like calculating performance, deleting records, etc. It is yet an incomplete work but the first part (accepting and storing details) are done. I have spent a lot of time behind this and the only thing I get is a nullPointerError. Sorry, but I have been asked to stick to the basics, so no glitzy code. I have used inheritance. The superclass is "Student".
public class Student {
int roll,age = 0; // Roll to be auto-updated
String cl,name;
// Marks variables now
int m_eng, m_math, m_physics, m_chem, m_bio = 0;
public Student(){
}
public Student(int a, String cla){
age = a;
cl = cla; // Assign values
}
void setMarks(int eng, int math, int phy, int chem, int bio){
m_eng = eng; m_math = math; m_physics = phy; m_chem = chem; m_bio = bio;
}
}
Here's the error:
java.lang.NullPointerException
at Application.accept_data(Application.java:35)
at Application.execute(Application.java:23)
at Application.input(Application.java:16)
at Application.main(Application.java:101)
Here is the code, though:
import java.util.Scanner;
public class Application extends Student {
static int n; static Scanner sc = new Scanner(System.in);
static Student s[];
void input(){
System.out.println("Enter the number of students: ");
n = sc.nextInt();
s = new Student[n]; // Create array for n students
System.out.println("Enter your choice: ");
System.out.println("1. Accept student's details ");
System.out.println("2. Display all records ");
System.out.println("3. Display data student-wise ");
System.out.println("4. Delete record");
System.out.println("5. Display performance status");
System.out.println("6. Exit");
execute();
}
static void execute(){
boolean correct = false;
while (!correct){
int op = sc.nextInt();
switch(op){
case 1: accept_data(); correct = true;
case 2: disp_data();correct = true;
case 3: disp_studentwise();correct = true;
case 4: del_record();correct = true;
case 5: performance();correct = true;
case 6: System.exit(0); correct = true;//Terminate
default: System.out.println("You must enter a choice. Kindly re-enter: ");correct = false;
}
}
}
static void accept_data(){
for (int i = 0; i<s.length; i++){
s[i].roll = i+1; //Autoupdate roll
System.out.println("Enter name: "); s[i].name = sc.nextLine();
System.out.println("Enter age: "); s[i].age = sc.nextInt(); // Refer to object prope.
System.out.println("Enter class: "); s[i].cl = sc.nextLine();
System.out.println("We're heading for marks entry!");
System.out.println("Enter marks in the following order: ENGLISH, MATH, PHYSICS, CHEMISTRY, BIOLOGY");
s[i].setMarks(sc.nextInt(),sc.nextInt(),sc.nextInt(),sc.nextInt(),sc.nextInt());
}
System.out.println("Thanks. Main menu, please enter your choice now: ");
execute();
}
static void disp_data(){
System.out.println("The system will display all stored information of students available.");
for (int i = 0; i<s.length; i++){
if (s[i].roll != -1){
continue; // In case record is deleted, it won't display
}
else {
printrec(i);
}
}
System.out.println("Main menu, please enter your choice: ");
execute();
}
static void disp_studentwise(){
System.out.println("Enter the roll number");
int r = sc.nextInt();
boolean ok = (r>s.length||r<0)?false:true;
while (!ok){
System.out.println("Incorrect roll. Please re-enter: ");
r = sc.nextInt();
if (r>s.length) ok = false;
else ok = true;
}
printrec(r-1);
System.out.println("Main menu, please enter your choice: ");
execute();
}
static void printrec(int n){
int i = n;
System.out.println("For roll number " + s[i].roll + ", details: ");
System.out.println("Name: " + s[i].name); System.out.println("Age: " + s[i].age);
System.out.println("Class: " + s[i].cl);
System.out.println("Subject \t Marks");
System.out.println("English: \t " + s[i].m_eng); // Display record with marks
System.out.println("Maths: \t " + s[i].m_math);
System.out.println("Physics: \t " + s[i].m_physics);
System.out.println("Chemistry: \t " + s[i].m_chem);
System.out.println("Biology: \t " + s[i].m_bio);
}
static void del_record(){
System.out.println("Enter the roll number you want to delete: ");
int rll = sc.nextInt();
for (int i = 0; i<s.length; i++){
if (rll == s[i].roll){
s[i].roll = -1; // Assign non-positive value to refer deleted items
}
}
}
static void performance(){
}
public static void main(String[] args){
Application ob = new Application();
ob.input(); // Start program
}
}
Can anyone point out what's going wrong? Why there's a problem with accepting details of students after pressing for the 1st option? It shows nullPointer on s[i].roll. Keep in mind that roll is autoupdated, and user doesn't intervene there. It serves as a primary key. An explanation would be beneficial, if possible of course, I am eager to learn. Thanks.
this :
s = new Student[n]; // Create array for n students
You are just creating an array of 'n' Student objects here ... that doesn't mean that your 'n' Students are initialized ... your array contains only 'null' values ...
you may want in your accept_data method do a :
for (int i = 0; i<s.length; i++){
s[i] = new Student();
s[i].roll = i+1; //Autoupdate roll
....
You are getting an NPE because you create an array of Students in your input method, but you never populate it with Student objects, so in accept_data, you're trying to access the roll field on a non-existent object.
You will need to fill in the array with new Student objects in your input method before you call accept_data.
I have an ArrayList of FlowerClass objects. Each of these FlowerClass objects has a name. I want to go through the ArrayList and count them. I want to display the amount of each. So if I have three FlowerClass objects named Rose, two named Daffodil, and one named Tulip...I want to display the following:
Found 3 Rose
Found 3 Daffodil
Found 3 Tulip
So far, I've gotten it to count correctly using two functions I made. The problem is that I iterate through the entire ArrayList...so it'll show me the results more than once. For example, if the user adds 3 Roses and 2 Daffodils...The output is like this:
Found 3 Roses
Found 3 Roses
Found 3 Roses
Found 2 Daffodils
Found 2 Daffodils
I know why the code does this but I don't know how to erase repeats of output. I also don't know how to implement Collections correctly. I've used Collections on an ArrayList of strings before...and it works. But this time I'd be using Collections on an ArrayList of Objects, and I want to check for the frequency of each specific name. Here is the main class:
import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
public class MainClass {
static ArrayList<FlowerClass> flowerPack = new ArrayList<FlowerClass>();
public static void main(String[] args){
Scanner input = new Scanner(System.in);
while(true){
System.out.println("1. Add flower to flowerpack.");
System.out.println("2. Remove flower from the flowerpack.");
System.out.println("3. Search for a flower in the flowerpack.");
System.out.println("4. Display the flowers in the flowerpack.");
System.out.println("5. Exit the program.");
int userChoice = input.nextInt();
switch(userChoice){
case 1:
addFlower();
break;
case 2:
searchFlower();
break;
case 3:
displayFlowers();
break;
case 4:
System.out.println("Goodbye!");
System.exit(0);
}
}
}
public static void addFlower(){
if (FlowerClass.numberFlowers() == 25){
System.out.println("There are 25 flowers in the flowerpack. Remove at least one in order to add more.");
return;
}
Scanner input = new Scanner(System.in);
System.out.println("What is the flower's name?");
String desiredName = input.nextLine();
System.out.println("What is the flower's color?");
String desiredColor = input.nextLine();
System.out.println("How many thorns does it have?");
Scanner input2 = new Scanner(System.in);
int desiredThorns = input2.nextInt();
System.out.println("What does it smell like?");
String desiredSmell = input.nextLine();
flowerPack.add(new FlowerClass(desiredName, desiredColor, desiredThorns, desiredSmell));
}
public static void searchFlower(){
System.out.println("Enter the flower you want to search for.");
Scanner input = new Scanner(System.in);
String userChoice = input.nextLine();
int occurrences = 0;
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if (userChoice.equals(name)){
occurrences++;
}
else if(occurrences == 0){
System.out.println("Match not found.");
return;
}
}
System.out.println("Found " + occurrences + " " + userChoice);
}
public static void searchFlower(String desiredFlower){
int occurrences = 0;
String userChoice = desiredFlower;
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if (userChoice.equals(name)){
occurrences++;
}
}
System.out.println("Found " + occurrences + " " + userChoice);
}
public static void displayFlowers(){
int repeats = 0;
/*for (FlowerClass flower: flowerPack){
System.out.println(flower.getName());
}
System.out.println("Number of flowers in pack: " + FlowerClass.numberFlowers());*/
//int occurrences = Collections.frequency(flowerPack, name);
//System.out.println(name + ": " + occurrences);
for (FlowerClass flower: flowerPack){
String name = flower.getName();
searchFlower(name);
}
}
}
Here is the FlowerClass:
public class FlowerClass {
public static int numberOfFlowers = 0;
public String flowerName = null;
public String flowerColor = null;
public int numberThorns = 0;
public String flowerSmell = null;
FlowerClass(){
}
FlowerClass(String desiredName, String desiredColor, int desiredThorns, String desiredSmell){
flowerName = desiredName;
flowerColor = desiredColor;
numberThorns = desiredThorns;
flowerSmell = desiredSmell;
numberOfFlowers++;
}
public void setName(String desiredName){
flowerName = desiredName;
}
public String getName(){
return flowerName;
}
public static int numberFlowers(){
return numberOfFlowers;
}
}
If you look at my last function in the main class, you'll see that I commented out the way I was attempting to implement Collections.frequency. I also tried making a multidimensional array of Strings and storing the names of the flowers and also the number of flowers in the arrays. This was counting everything correctly but I wasn't sure how to display the names alongside the counts. It was getting very messy so I abandoned that attempt for now in favor of trying these other two options. If I can find a way to erase repeated lines of output (or if I can find a way to get Collections to work) then I won't need to tinker with the multidimensional array.
Any tips would be very much appreciated. Thank you for your time.
Interesting code, but it doesn't work the way I would do it.
In this current case as you've done it, you would need to keep track of the flower names you have already encountered:
public static void displayFlowers(){
//int repeats = 0;
List<String> displayedFlowerTypes = new ArrayList<String>();
for (FlowerClass flower: flowerPack){
String name = flower.getName();
if(!displayedFlowerTypes.contains(name))
{
displayedFlowerTypes.add(name);
searchFlower(name);
}
}
}
What I would rather do is maintain a Map that keeps track of the counts of the flower types, and just obtain the numbers for the types from that:
public class MainClass {
static List<FlowerClass> flowerPack = new ArrayList<FlowerClass>();
static Map<String, Integer> flowerCount = new HashMap<String, Integer>();
public static void addFlower() {
if (FlowerClass.numberFlowers() == 25) {
System.out.println("There are 25 flowers in the flowerpack. Remove at least one in order to add more.");
return;
}
Scanner input = new Scanner(System.in);
System.out.println("What is the flower's name?");
String desiredName = input.nextLine();
System.out.println("What is the flower's color?");
String desiredColor = input.nextLine();
System.out.println("How many thorns does it have?");
Scanner input2 = new Scanner(System.in);
int desiredThorns = input2.nextInt();
System.out.println("What does it smell like?");
String desiredSmell = input.nextLine();
flowerPack.add(new FlowerClass(desiredName, desiredColor, desiredThorns, desiredSmell));
if(!flowerCount.containsKey(desiredName))
{
flowerCount.put(desiredName, 1);
}
else
{
int currentCount = flowerCount.get(desiredName);
flowerCount.put(desiredName, currentCount+1));
}
}
That way, you could just display the flowers as the following:
public static void displayFlowers() {
for (String name : flowerCount.keySet()) {
//searchFlower(name);
System.out.println("Found " + flowerCount.get(name) + " " + name);
}
}
You could put your Flower(s) in a Set. But the easiest solution I can think of is to sort your flowers. So first, implement a Comparator<FlowerClass>
public static class FlowerComparator implements Comparator<FlowerClass> {
#Override
public int compare(FlowerClass o1, FlowerClass o2) {
return o1.getName().compareTo(o2.getName());
}
}
Then you can sort with Collections.sort(List, Comparator)
FlowerComparator flowerComparator = new FlowerComparator();
Collections.sort(flowerPack, flowerComparator);
And then your for loop needs to be something like this (to stop searching for the same flower),
String lastName = null;
for (int i = 0; i < flowerPack.size(); i++){
FlowerClass flower = flowerPack.get(i);
String name = flower.getName();
if (lastName == null || !lastName.equals(name)) {
lastName = name;
searchFlower(name); // or return the number found, and then add that count to i.
}
}
How can I sort this array based on user input? While using a constructor, I am returning values to the create the output. What I'd like to do is after receiving how the user would like to arrange his/her inputs, I'd like to perform something like an Arrays.sort(books[x].getBook());
But this does not work. Is there a way to arrange the returned values for each input? The following is the error I receive upon using the code below within each if statement, although getBooks() is very well in existence:
Error log
LibraryBookSort.java:56: error: cannot find symbol
Arrays.sort(books[x].getBooks());
^
symbol: method getBooks()
location: class LibraryBook
1 error
Code
public class LibraryBookSort {
public static void main(String[] args) {
LibraryBook[] books = new LibraryBook[5];
for (int x = 0; x < 5; x++) {
books[x] = new LibraryBook();
}
Scanner input = new Scanner(System.in);
for (int x = 0; x < 5; x++) {
// Get title
System.out.print("Enter the title of a book: ");
String title = input.nextLine();
books[x].setBook(title);
// Get author
System.out.print("Enter the author of this book: ");
String author = input.nextLine();
books[x].setAuthor(title);
// Get page count
System.out.print("Enter the number of pages for this book: ");
int pages = input.nextInt();
books[x].setPages(pages);
input.nextLine();
}
System.out.println("How would you like to organize your values?");
System.out.println("Sort by title > Enter 1: ");
System.out.println("Sort by author's last name > Enter 2: ");
System.out.print("Sort by page count > Enter 3: ");
int sortBy = input.nextInt();
// Sort by title
if(sortBy == 1) {
//????;
}
// Sort by author
else if(sortBy == 2) {
//????;
}
// Sort by page count
else if(sortBy == 3) {
//????;
}
// Print sorted array >> Use of constructor
for(int x = 0; x < 5; x++) {
System.out.println();
System.out.println("Book ");
System.out.println("Title: " + books[x].getBook());
System.out.println("Author: " + books[x].getAuthor());
System.out.println("Page Count: " + books[x].getPages());
}}}
The following will arrange my inputs using a comparator. However, the question remains, is there another approach to sorting this data outside of using a comparator?
class TitleComparator implements Comparator {
public int compare(Object book1, Object book2) {
String title1 = ((LibraryBook) book1).getBook();
String title2 = ((LibraryBook) book2).getBook();
return title1.compareTo(title2);
}}
I tried to add like this and it is working. Store the books inside the collection. So that you can make use of Collections.sort function and Comparator.
LibraryBookSort.java
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class LibraryBookSort {
private static ArrayList<LibraryBook> list;
public static void main(String[] args) {
LibraryBook[] books = new LibraryBook[5];
for (int x = 0; x < 5; x++) {
books[x] = new LibraryBook();
}
Scanner input = new Scanner(System.in);
list = new ArrayList<LibraryBook>();
for (int x = 0; x < 5; x++) {
// Get title
System.out.print("Enter the title of a book: ");
String title = input.nextLine();
books[x].setBook(title);
// Get author
System.out.print("Enter the author of this book: ");
String author = input.nextLine();
books[x].setAuthor(title);
// Get page count
System.out.print("Enter the number of pages for this book: ");
int pages = input.nextInt();
books[x].setPages(pages);
list.add(books[x]);
input.nextLine();
}
System.out.println("How would you like to organize your values?");
System.out.println("Sort by title > Enter 1: ");
System.out.println("Sort by author's last name > Enter 2: ");
System.out.print("Sort by page count > Enter 3: ");
int sortBy = input.nextInt();
// Sort by title
if(sortBy == 1) {
Collections.sort(list,new TitleComparator());
}
// Sort by author
else if(sortBy == 2) {
//????;
}
// Sort by page count
else if(sortBy == 3) {
//????;
}
for(LibraryBook st: list){
System.out.println(st.title+" "+st.author+" "+st.pages);
}
}}
Also added another class TitleComparator.java.
import java.util.Comparator;
public class TitleComparator implements Comparator <LibraryBook>{
#Override
public int compare(LibraryBook arg0, LibraryBook arg1) {
return arg0.title.compareTo(arg1.title);
}
}
This is for sort books based on the title. You can also add PageComparator and AuthorComparator for the other two options.