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Collections.sort() error occuring while sorting ArrayList [closed]

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I'm trying to sort by name ArrayList elements but I couldn't solve problem . . . . . .
Could someone help?
ERROR At case 4: Collections.sort(contact);
ERROR "Required type: List Provided: List reason: no
instance(s) of type variable(s) T exist so that Data conforms to
Comparable<? super T>"
below code works fine without sort
public class AddressBook {
private static List<Data> contact = new ArrayList<Data>();
public static void main(String[] args) {
AddressBook addressBook = new AddressBook();
Scanner sc = new Scanner(System.in);
int menu;
String choice;
String choice2;
System.out.println(" =========================== ");
System.out.println(" | 0. Exit. |");
System.out.println(" | 1. Add contact. |");
System.out.println(" =========================== ");
try
{
menu = sc.nextInt();
while (menu != 0) {
switch (menu) {
case 1:
while (menu != 2) {
System.out.println("Enter First Name: ");
String firstName = sc.next();
System.out.println("Enter Last Name: ");
String lastName = sc.next();
System.out.println("Enter Phone: ");
String homePhone = sc.next();
if (homePhone.length()!=11 || !homePhone.startsWith("8")) {
System.out.println("Number should start with '8' and has '11' digit" );
}else {
System.out.println("Enter Email: ");
String personalWebSite = sc.next();
contact.add(new Data(firstName, lastName,
homePhone, personalWebSite));
}
System.out
.println("Would you like to add someone else? 1: Yes, 2: No");
menu = sc.nextInt();
}
break;
case 2:
System.out
.println("Enter First Name of contact that you would like to edit: ");
choice = sc.next();
addressBook.deleteByFirstName(choice);
System.out.println("Enter First Name: ");
String firstName = sc.next().toUpperCase();
System.out.println("Enter Last Name: ");
String lastName = sc.next();
System.out.println("Enter Phone: ");
String homePhone = sc.next();
System.out.println("Enter Email: ");
String personalWebSite = sc.next();
contact.add(new Data(firstName, lastName,
homePhone, personalWebSite));
break;
case 3:
System.out.println("------------------");
System.out.println("1. Search number: ");
System.out.println("2. Search name: ");
System.out.println("------------------");
int search= sc.nextInt();
if(search==1) {
System.out
.println("Enter Number of contact: ");
choice2 = sc.next();
addressBook.searchByPhoneNumber(choice2);
break;
}else {
System.out
.println("Enter First Name of contact: ");
choice = sc.next();
addressBook.searchByFirstName(choice);
break;
}
case 4:
Collections.sort(contact);
//ERROR occurring here
case 5:
System.out.println("This is a list of every contact");
System.out.println(addressBook.contact);
break;
case 6:
System.out.println("------------------");
System.out.println("1. Delete by name: ");
System.out.println("2. Delete all: ");
System.out.println("------------------");
int del= sc.nextInt();
if(del==1){
System.out
.println("Enter First Name of contact that you would like to delete: ");
choice = sc.next();
addressBook.deleteByFirstName(choice);
break;
}else{
System.out.println("Successfully Deleted");
System.out.println("");
contact.clear();
}
break;
default:
throw new IllegalStateException("Unexpected value: " + menu);
}
System.out.println(" =========================== ");
System.out.println(" | 0. Exit. |");
System.out.println(" | 1. Add contact. |");
System.out.println(" =========================== ");
menu = sc.nextInt();
}
}
catch(InputMismatchException exception)
{
System.out.println("This is not an integer");
}
System.out.println("Good-Bye!");
}
private void searchByFirstName(String firstName) {
for (Iterator<Data> iterator = contact.iterator(); iterator.hasNext();) {
Data temp = iterator.next();
if (temp.getFirstName().equalsIgnoreCase(firstName)) {
System.out.println(temp);
return;
}
}
System.out.println("No contact with first name " + firstName
+ " was found.");
}
private void searchByPhoneNumber(String homePhone) {
for (Iterator<Data> iterator = contact.iterator(); iterator.hasNext();) {
Data temp = iterator.next();
if (temp.getHomePhone().equalsIgnoreCase(homePhone)) {
System.out.println(temp);
return;
}
}
System.out.println("No contact with number " + homePhone
+ " was found.");
}
private void deleteByFirstName(String firstName) {
for (Iterator<Data> iterator = contact.iterator(); iterator.hasNext();) {
Data temp = iterator.next();
if (temp.getFirstName().equalsIgnoreCase(firstName)) {
iterator.remove();
return;
}
}
System.out.println("No contact with first name " + firstName
+ " was found.");
}
private void deleteAll(String all) {
for (Iterator<Data> iterator = contact.iterator(); iterator.hasNext();) {
iterator.remove();
return;
}
System.out.println("Deleting...");
}
private static int[] selectionSortAlg(int[] a, int n) {
for (int i = 0; i < n - 1; i++) {
int iMin = i;
for (int j = i + 1; j < n; j++) {
if (a[j] < a[iMin]) {
iMin = j; // index of smallest element
}
}
int temp = a[i];
a[i] = a[iMin];
a[iMin] = temp;
System.out.println("Pass..." + i + "..." + Arrays.toString(a));
}
return a;
}
public static class Data {
private String firstName = null;
private String lastName = null;
private String homePhone = null;
private String personalWebSite = null;
public Data(String firstName,String lastName, String homePhone, String personalWebSite) {
this.firstName = firstName;
this.lastName = lastName;
this.homePhone = homePhone;
this.personalWebSite = personalWebSite;
}
public String getFirstName() {
return firstName;
}
public String getHomePhone() {
return homePhone;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String toString() {
return String.format(firstName+" "+lastName+" "+homePhone+" "+personalWebSite);
}
}
}
class T {
private String firstName = null;
private String lastName = null;
private String homePhone = null;
private String personalWebSite = null;
public T(String firstName,String lastName, String homePhone, String personalWebSite) {
this.firstName = firstName;
this.lastName = lastName;
this.homePhone = homePhone;
this.personalWebSite = personalWebSite;
}
public String getFirstName() {
return firstName;
}
public String getHomePhone() {
return homePhone;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String toString() {
return String.format(firstName+" "+lastName+" "+homePhone+" "+personalWebSite);
}
}

I am not quite sure, but I think you need to do this(in your case 4):
Collections.sort(contact, new Comparator<Data>() {
#Override
public int compare(Data contact1, Data contact2) {
return contact1.getFirstName().compareTo(contact2.getFirstName());
}
});
Give it a try, I had used it somewhere else, and it worked. Hope it helps. Cheers :)

Use in this way
contact.sort( Comparator.comparing(Data::getFirstName) );

You have 2 options whether implement Comparable or provide comparator to sorting function, i.e.
Collections.sort(contact, (d1,d2) -> d1.firstName.compareTo(d2.firstName));
or
contact.sort((d1,d2) -> d1.firstName.compareTo(d2.firstName));

Your class Data you implement comparable, look at here:
https://www.geeksforgeeks.org/comparable-vs-comparator-in-java/
public static class Data implements Comparable<Data>
...
public int compareTo(Data m) {
...
}

Either pass a comparator in sort method or make Data class implement Comparable interface and implement compareTo()
#GiorgosDev gave an example in which data class is expected to implement comparable interface.

Either implement comparable in Data class or pass comparator in sort method. Example Collections.sort(contact, Comparator.comparing(Data::getFirstName));

ArrayLists (Removing and Changing Elements)

Hello everyone I am an amateur in Java and had some specific questions about a program using ArrayLists. The program is made up of several classes, and its purpose is to add, change, remove, and display friends from a Phone Book. I have the add and display methods done, but I'm having trouble with the remove and change method. I saw a similar case on this site, but it did not help me solve my problems. Any help at all would be much appreciated. This is what I have so far:
package bestfriends;
import java.util.Scanner;
import java.util.ArrayList;
public class BFFHelper
{
ArrayList<BestFriends> myBFFs;
Scanner keyboard = new Scanner(System.in);
public BFFHelper()
{
myBFFs = new ArrayList<BestFriends>();
}
public void addABFF()
{
System.out.println("Enter a first name: ");
String firstName = keyboard.next();
System.out.println("Enter a last name: ");
String lastName = keyboard.next();
System.out.println("Enter a nick name: ");
String nickName = keyboard.next();
System.out.println("Enter a phone number: ");
String cellPhone = keyboard.next();
BestFriends aBFF = new BestFriends(firstName, lastName, nickName, cellPhone);
myBFFs.add(aBFF);
}
public void changeABFF()
{
System.out.println("I am in changeBFF");
}
public void displayABFF()
{
System.out.println("My Best Friends Phonebook is: ");
System.out.println(myBFFs);
}
public void removeABFF()
{
System.out.print("Enter a friend's name to be removed: ");
int i = 0;
boolean found = false;
while (i < myBFFs.size() && !found)
{
if(firstName.equalsIgnoreCase(myBFFs.get(i).getFirstName()) && lastName.equalsIgnoreCase(myBFFs.get(i).getLastName()))
{
found = true;
}
else
i++;
}
}
}
That was my Helper Class, for which I'm having trouble with the removeABFF method, and still need to create a changeABFF method from scratch. Next is my main class:
package bestfriends;
import java.util.Scanner;
public class BFFPhoneBook
{
public static void main(String args[])
{
int menuOption = 0;
Scanner keyboard = new Scanner(System.in);
BFFHelper myHelper = new BFFHelper();
do
{
System.out.println("1. Add a Friend");
System.out.println("2. Change a Friend");
System.out.println("3. Remove a Friend");
System.out.println("4. Display a Friend");
System.out.println("5. Exit");
System.out.print("Enter your selection: ");
menuOption = keyboard.nextInt();
switch (menuOption)
{
case 1:
myHelper.addABFF();
break;
case 2:
myHelper.changeABFF();
break;
case 3:
myHelper.removeABFF();
break;
case 4:
myHelper.displayABFF();
break;
case 5:
break;
default:
System.out.println("Invalid option. Enter 1 - 5");
}
} while (menuOption != 5);
}
}
This is my last class:
package bestfriends;
public class BestFriends {
private static int friendNumber = 0;
private int friendIdNumber;
String firstName;
private String lastName;
private String nickName;
private String cellPhoneNumber;
public BestFriends (String aFirstName, String aLastName, String aNickName, String aCellPhone)
{
firstName = aFirstName;
lastName = aLastName;
nickName = aNickName;
cellPhoneNumber = aCellPhone;
friendIdNumber = ++friendNumber;
// friendIdNumber = friendNumber++;
}
public boolean equals(Object aFriend)
{
if (aFriend instanceof BestFriends )
{
BestFriends myFriend = (BestFriends) aFriend;
if (lastName.equals(myFriend.lastName) && firstName.equals(myFriend.firstName))
return true;
else
return false;
}
else
return false;
}
public String getFirstName()
{
return firstName;
}
public String getLastName()
{
return lastName;
}
public String getNickName()
{
return nickName;
}
public String getCellPhone()
{
return cellPhoneNumber;
}
public int getFriendId()
{
return friendIdNumber;
}
public String toString()
{
return friendIdNumber + ". " + firstName + " (" + nickName + ") " + lastName + "\n" + cellPhoneNumber + "\n";
}
}

To explore and manipulate a arraylist an iterator is used
the object lacks the Setters
declare variables
ArrayList<BestFriends> myBFFs;
Scanner keyboard = new Scanner(System.in);
BestFriends best;
public BFFHelper()
{
myBFFs = new ArrayList<BestFriends>();
best= new BestFriends();
}
Delete
public void removeABFF()
{
System.out.print("Enter a friend's name to be removed: ");
String name= keyboard.next().toLowerCase();// entry name to be removed
Iterator<BestFriends> nameIter = myBFFs.iterator(); //manipulate ArrayList
while (nameIter.hasNext()){
best = nameIter.next(); // obtained object list
if (best.getNickName().trim().toLowerCase().equals(name)){ // if equals name
nameIter.remove(best); // remove to arraylist
}
}
}
Update
public void changeABFF()
{
System.out.print("Enter a friend's name to be change: ");
String name= keyboard.next().toLowerCase().trim();//entry name to be update
Iterator<BestFriends> nameIter = myBFFs.iterator();
while (nameIter.hasNext()){
best = nameIter.next();
if (best.getNickName().trim().toLowerCase().equals(name)){// if equals name
best.setNickName("NEW DATE");//update data with new data Setters
....
}
}
}

In your remove method you do not accept any input of the values
public void removeABFF()
{
System.out.print("Enter a friend's name to be removed: ");
int i = 0;
boolean found = false;
while (i < myBFFs.size() && !found)
....
As you are using firstNamer and lastName to find the object you needs these values
System.out.println("Enter a first name: ");
String firstName = keyboard.next();
System.out.println("Enter a last name: ");
String lastName = keyboard.next();

Java arrayList comparison

Could anybody tell me how to list some data in an arrayList according to the integer value that each component of the ArrayList has? This is my main class
import java.util.Scanner;
import java.io.*;
import java.util.Collections;
import java.util.ArrayList;
public class StudentDriver {
public static void main(String[] args) throws IOException {
Scanner scan, urlScan, fileScan;
String url, file;
int count = 0;
scan = new Scanner(System.in);
System.out.println("Enter the name of the file");
fileScan = new Scanner(new File("Data.csv"));
ArrayList<Student> studentList = new ArrayList<Student>();
while(fileScan.hasNext()){
url = fileScan.nextLine();
urlScan = new Scanner(url);
urlScan.useDelimiter(",");
count++;
while(urlScan.hasNext()){
String name = urlScan.next();
String last = urlScan.next();
int score = urlScan.nextInt();
Student e = new Student(name,last, score);
studentList.add(e);
}
}
System.out.println("The file has data for" +count+ "instances");
int option;
do{
System.out.println("********");
System.out.println("Options:");
System.out.println("********\n1. List \n2. Add Student \n3.Delete Student \n4. Exit \n******** ");
System.out.print("Select option: ");
option = scan.nextInt();
if(option == 1){
int index = 0;
while(index<studentList.size()){
System.out.println(studentList.get(index));
index++;
}
}
else if(option == 2){
System.out.print("Enter the name of the student: ");
String newName = scan.next();
System.out.print("Enter the last name of the student: ");
String newLastName = scan.next();
System.out.print("Enter the exam score of the student: ");
int newScore = scan.nextInt();
Student b = new Student(newName, newLastName, newScore);
studentList.add(b);}
else if(option == 3){
System.out.print("Enter the name of the student to remove: ");
String remove = scan.next();
System.out.print("Enter the last name of the student: ");
String remove1 = scan.next();
int location = studentList.indexOf(remove);
location = studentList.indexOf(remove1);
studentList.remove(location);
}
}while(option!=4 && option <4);
}//main
}//class
And this is the other class
public class Student implements Comparable<Student>{
String firstName, lastName;
int score;
public Student(String firstName, String lastName, int score){
this.firstName = firstName;
this.lastName = lastName;
this.score = score;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
public String toString(){
return firstName + " " + lastName + ", exam score is "+ score;
}
#Override
public int compareTo(Student c) {
return score-c.getScore();
}
}
As you can see, up to now I have created the class where my compare method is but I have difficulties on using it. Also I have had difficulties on deleting one of the Array List parts by just writing the name and last name of the student. If somebody would help me, I would be very thankful.

well you can change your compareTo method as
public int compareTo(Student another)
{
if (this.score > another.score)
return -1;
if (this.score < another.score)
return 1;
else
return 0;
}
this should show it as decreasing order you can change the operator
than use whereever you want to sort it
Collections.sort(studentList)
Also if you don't want to use Collections.sort() method I can show you how you can write it with for loop under add option
Student newStd = new Student(name, last, score);
for(int i=0;studentList.size()>i;i++)
{
int size = studentList.size();
if(newStd.compareToCustom(studentList.get(i))>0)
{
studentList.add(i, newStd);
break;
}
else if(newStd.compareToCustom(studentList.get(size-1))<0)
{
studentList.add(studentList.size(), newStd);
break;
}
else if(newStd.compareToCustom(studentList.get(i))==0)
{
studentList.add(i++, newStd);
break;
}
}
for the remove part you can use
else if ( option == 3)
{
System.out.print("Enter the first name of student will be deleted: ");
String removeName = scan.next();
System.out.print("Enter the last name of student will be deleted: ");
String removeLastName = scan.next();
for ( int i = 0; i < studentList.size(); i++)
{
Student deleted = studentList.get(i);
if ( deleted.getFirstName().toLowerCase().equals(removeName.toLowerCase()) && deleted.getLastName().toLowerCase().equals(removeLastName.toLowerCase()))
{
studentList.remove(i);
System.out.println("The student has been deleted.");
break;
}
else
{
System.out.println("This student is not found");
break;
}
}
}

Basically what you want is an ordered collection. As #duffymo has stated, think about a creating a custom Comparator using your score.
There is plenty of info here

In terms of deleting students from the list.
The studentList is a list containing Student objects.
This means that the follow code:
System.out.print("Enter the name of the student to remove: ");
String remove = scan.next();
System.out.print("Enter the last name of the student: ");
String remove1 = scan.next();
int location = studentList.indexOf(remove);
Tries to find the index of a Student given the first name. This will return -1 as you're searching for a String and not a Student object.
Instead you have to iterate through your studentList and compare the first and last name of each Student element with the values of remove and remove1.
for(Student student : studentList) {
if(student.getFirstName.equals(remove) && student.getLastName.equals(remove1)) {
// remove the student.
}
}
Also you could consider giving each Student an ID as an unique identifier.

try this to sort studentList
Collections.sort(studentList, new Comparator<Student>()
{
#Override
public int compare(Student x, Student y)
{
if(x.score >= y.score)
return 1;
else
return -1;
}
});

AddressBook Program Remove And Search Method Null Pointer Exceptions

EDIT5:My remove() method asks for a name to remove, and no matter what name I enter in it will delete the latest name in the array. I'm not sure how to fix this, and my search array will ask for a name and then declare a Null Pointer Exception error. The rest of my code is provided below.
case 3: //Remove a contact
System.out.print("Full name to remove: ");
Scanner rs = new Scanner(System.in);
String deleteName = rs.nextLine();
a1.remove(deleteName);
break;
case 4: //search a contact
System.out.print("Full name to search: ");
Scanner ss = new Scanner(System.in);
String searchName = ss.nextLine();
a1.search(searchName);
break;
EDIT4: Figured out the initialization problem.. can't believe I missed something so simple. My program now works nearly perfect, besides for my remove function, which encounters a null Pointer exception. Can someone explain to me why this happens? Also I've updated the code
EDIT3: I now have nothing yelling at me in my Contact and AddressBook classes. I just need to know how to make my methods in main work. As someone pointed out in the comments I need to initialize my methods and classes. Can someone please tell me where I need to put my constructor so these methods will work? I have them placed in multiple areas of my program already to no avail.
I'm working on an AddressBook program for my java class. I've constructed everything, but my methods in other classes are giving me some difficulty(I made all my methods public and my class specific variables private). Also I would like some feedback on how I constructed my methods. I was given a rough outline of what methods to use here:
Contact
-firstName:String
-lastName:String
-phone:String
+Contact(firstName:String,lastName:String, phone:String)
+getFullName():String
+getLastName():String
+getPhone():String
+setFirstName(firstName:String):void
+setLastName(lastName:String):void
+setPhone(phone:String):void
+equals(o:Object):boolean #currently not sure how to do this method
+toString():String
AddressBook class
-contacts:Contact[]
- count:int;
-fileName:String
+AddressBook(fileName:String)
+add(Contact c):boolean
+remove(fullName:String):boolean
+search(fullName:String):Contact
+display():void
+load():boolean
+save():boolean
+search(String fullName):boolean
Here is my code:
Contact class code:
public class Contact {
private String firstName;
private String lastName;
private String phone;
public Contact(String firstName, String lastName, String phone) {
this.firstName = firstName;
this.lastName = lastName;
this.phone = phone;
}
public String getFullName(){
return firstName + " " + lastName;
}
public String getFirstName(){
return firstName;
}
public String getLastName(){
return lastName;
}
public String getPhone(){
return phone;
}
public void setFirstName(String firstName){
this.firstName = firstName;
}
public void setLastName(String lastName){
this.lastName = lastName;
}
public void setPhone(String phone){
this.phone = phone;
}
/*public boolean equals(Contact o){ //not sure how to use this method, tips/suggestions?
}*/
public String toString(){
return firstName + ":" + lastName + ":" + phone;
}
}
AddressBook Class
import java.io.File;
import java.io.FileWriter;
import java.util.Scanner;
public class AddressBook {
private Contact[] contacts = new Contact[100];
private int count = 0;
private String fileName;
public AddressBook(String fileName) {
this.fileName = fileName;
}
public boolean add(Contact c) {
// Checks to see if the array is full
if (count > 99) {
return false;
}
// Adds the new contact into the array
contacts[count] = c;
// increment count
count++;
return true;
}
public boolean remove(String deleteName) { //switched fullName to deleteName to avoid duplicate variable problems
for (int i = 0; i < count; i++) {
if(contacts[i].getFullName() == deleteName) {
contacts[i] = null;
contacts[i] = contacts[i-1];
}
}
count--;
return true;
}
public Contact search(String searchName){ //switched fullName to searchName to avoid duplicate variable problems in the main class
for(int i = 0; i < contacts.length; i++){
if (contacts[i].getFullName() == searchName) {
return contacts[i];
}
} return null;
}
public void display() {
System.out.println("Name Phone Number"); //setting up the format for displaying contacts
System.out.println("-------------------------------");
for (int i = 0; i < count; i++) { //for loop printing out and displaying contacts
System.out.println(contacts[i].getFirstName() + " "
+ contacts[i].getLastName() + "\t\t"
+ contacts[i].getPhone());
}
System.out.println("-------------------------------");
}
public boolean load() {
//reads the file address.txt and loads it
try {
File fr = new File(fileName);
Scanner s = new Scanner(fr);
while(s.hasNextLine()) {
String oStore = s.nextLine(); //Storing the line of string here so it can be split
String[] aStore = oStore.split(":"); //Splits oStore up and inputs the values into constructor
contacts[count]=new Contact(aStore[0], aStore[1], aStore[2]);
count++;//increments count each contact
}
s.close();
return true;
} catch (Exception e){
return false;
}
}
public boolean save() {
// Writes the new contact into the file address.txt
try {
FileWriter fw = new FileWriter(fileName);
for (int i = 0; i < contacts.length; i++) {
fw.write(contacts[i].getFirstName() + ":"
+ contacts[i].getLastName() + ":"
+ contacts[i].getPhone() + "\n");
}
fw.close();
} catch (Exception e) {
return false;
}
return true;
}
/*public boolean search(String searchName) { //switched fullName to searchName to avoid duplicate variable problems in the main class
for(int i = 0; i <contacts.length; i++){
if (contacts[i].getFullName() == searchName) {
return contacts[i].getFullName() + contacts[i].getPhone();
}
}
return true;
}*/
}
Main Class
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
AddressBook a1 = new AddressBook("address.txt");
boolean pQuit = false; //boolean value to end the program
a1.load();
System.out.println("Welcome. Address book is loaded.");
System.out.println("");
do{
//Setting up the initial menu
System.out.println("What would you like to do?");
System.out.println("1) Display all contacts");
System.out.println("2) Add a contact");
System.out.println("3) Remove a contact");
System.out.println("4) Search a contact");
System.out.println("5) Exit");
System.out.println("Your choice: ");
Scanner s = new Scanner(System.in); //Scanner for user's choice
int choice = s.nextInt(); //User picks menu choice
System.out.println("\n");//line break
switch(choice){
case 1: //Display all contacts
a1.display();
break;
case 2: //Add a contact
System.out.print("First name:");
String firstName = s.next(); //Stores first name in firstName
System.out.print("Last name:");
String lastName = s.next(); //Stores last name in lastName
System.out.print("Phone number:");
String phone = s.next();
a1.add(new Contact(firstName,lastName,phone));
System.out.println("Contact added.");
break;
case 3: //Remove a contact
System.out.print("Full name to remove: ");
Scanner rs = new Scanner(System.in);
String deleteName = rs.nextLine();
a1.remove(deleteName);
break;
case 4: //search a contact
System.out.print("Full name to search: ");
Scanner ss = new Scanner(System.in);
String searchName = ss.nextLine();
a1.search(searchName);
break;
case 5: //exit the program
a1.save();
System.out.println("Addres book is saved to file.");
pQuit = true;
break;
default:
System.out.println("That is not a valid input.");
}
}while (pQuit == false);
}
}
Right now in my main method none of the methods I have called work because they are undefined. Same instance happened when I tried to use the contacts array in my +equals(o:Object):boolean method. All help is much appreciated, and if you see anything wrong in my methods or anything at all I could fix and improve please let me know!
Thanks in advance for the help.
EDIT1: Also please note the two search methods I was given. I pretty much constructed the same code for both. Eclipse right now is yelling at me telling me to change the name of the methods. I would like to know if I constructed the methods incorrectly, or why I would be given two of the same named methods to use in my program.
EDIT2: Updated to my new code. Changed a couple things, methods still do not work though.

Trouble with calling methods from other classes

My code is not compiling and my biggest issue is that line 32 compiles but 42 does not and the methods they come from are written exactly the same. The error message is error cannot find symbol.
import java.util.*;
import java.text.*;
public class CourseApp{
public static void main(String[] args){
Scanner s = new Scanner (System.in);
DecimalFormat df = new DecimalFormat("$0.00");
int initialSize;
boolean q = true;
System.out.println("Enter how many courses you would like to enter info rmation for? ");
try{initialSize = s.nextInt();}
catch(NumberFormatException sonic){
while(initialSize <= 0){
System.out.println("Please enter an integer greater than 0 (ie5). ");
initialSize = s.nextInt();}}
ArrayList <Course> courseArrayList = new ArrayList<Course> (initialSize);
String number="";
String name="";
String instr="";
String text="";
for (int i = 0; i < initialSize; i++){
courseArrayList.add(new Course(number, name, instr, text));
System.out.println("Enter in course information. ");
do{
courseArrayList.get(i).setNumber("");
System.out.println("Please enter the course number: ");
courseArrayList.get(i).setNumber(s.nextLine());
}while(courseArrayList.get(i).getNumber().equals(""));
do{
courseArrayList.get(i).setName("");
System.out.println("Please enter the course name: ");
courseArrayList.get(i).setName(s.nextLine());
}while(courseArrayList.get(i).getName().equals(""));
do{
courseArrayList.get(i).setLastName("");
System.out.println("Please enter the Instructor's last name: ");
courseArrayList.get(i).setLastName(s.nextLine());
}while(courseArrayList.get(i).getLastName().equals(""));
do{
courseArrayList.get(i).setFirstName("");
System.out.println("Please enter the Instructor's first name: ");
courseArrayList.get(i).setFirstName(s.nextLine());
}while(courseArrayList.get(i).getFirstName().equals(""));
do{
courseArrayList.get(i).setUserName("");
System.out.println("Please enter the Instructor's user name: ");
courseArrayList.get(i).setUserName(s.nextLine());
}while(courseArrayList.get(i).getUserName().equals(""));
String[] instrr = new String[3];
instrr[0]=courseArrayList.get(i).getLastName()+", ";
instrr[1]=courseArrayList.get(i).getFirstName()+"\n";
instrr[2]=courseArrayList.get(i).getUserName()+"#K-State.ksu";
instr = instrr[0]+instrr[1]+instrr[2];
System.out.println("Please enter the required text book's title: ");
courseArrayList.get(i).setTitle(s.nextLine());
System.out.println("Please enter the required text book's author: ");
courseArrayList.get(i).setAuthor(s.nextLine());
System.out.println("Please enter the required text book's price: ");
try{courseArrayList.get(i).setPrice(s.nextDouble());}
catch(NumberFormatException shadow){
while(courseArrayList.get(i).setPrice(s.nextDouble()) < 0){
System.out.println("Please enter a positive numerical value. ");
courseArrayList.get(i).setPrice(s.nextDouble());}}
String[] textt = new String[3];
textt[0]=courseArrayList.get(i).getTitle()+"\n";
textt[1]=courseArrayList.get(i).getAuthor()+"\n";
textt[2]=df.format(courseArrayList.get(i).getPrice())+"\n";
text = textt[0]+textt[1]+textt[2];}
for (int i = 0; i < initialSize; i++){
System.out.println("Press enter to display each of the courses");
s.nextLine();
courseArrayList.get(i).toString();}
System.out.println("Please enter a course number");
String a = s.nextLine();
for (int i = 0; i < initialSize; i++){
if (a.equals(courseArrayList.get(i).getNumber())){
courseArrayList.remove(i);}
else if (! a.equals(courseArrayList.get(initialSize-1).getNumber())){
do {
System.out.println("Course number not found.");
System.out.println("Please enter a valid course number: ");
a = s.nextLine();
for (int j = 0; j < initialSize; j++){
if (a.equals(courseArrayList.get(j).getNumber())){
q=false;
courseArrayList.remove(j);}}
} while (q=true);}
else {}}
for (int i = 0; i < initialSize; i++){
System.out.println("Press enter to display each of the courses");
s.nextLine();
courseArrayList.get(i).toString();}}}
this is from a different class and this part does not compile
public void setLastName(String lname){
lastName=lname;}
the instructor class is:
public class Instructor
{
private String lastName; // Last name
private String firstName; // First name
private String userName; // Username ID
public Instructor(String lname, String fname, String un){
lastName = lname;
firstName = fname;
userName = un;}
public Instructor(Instructor object2){
lastName = object2.lastName;
firstName = object2.firstName;
userName = object2.userName;}
public void setLastName(String lname){
lastName=lname;}
public String getLastName(){
return lastName;}
public void setFirstName(String fname){
firstName=fname;}
public String getFirstName(){
return firstName;}
public void setUserName(String un){
userName=un;}
public String getUserName(){
return userName;}
public String toString()
{
return str;
}
}
this is from a different class and this part does compile
public void setName(String name){
courseName=name;}
the course class is:
public class Course
{
private String courseNumber; // e.g. CIS 200
private String courseName; // e.g. Programming Fundamentals
private Instructor instructor; // Course instructor (object)
private TextBook textBook; // Required Course textbook (object)
public Course(String number, String name, String instr, String text){
courseNumber = number;
courseName = name;
instructor = new Instructor(instr);
textBook = new TextBook(text);}
public String getName(){
return courseName;}
public void setName(String name){
courseName=name;}
public String getNumber(){
return courseNumber;}
public void setNumber(String number){
courseNumber=number;}
public Instructor getInstructor(){return new Instructor(instructor);}
/**getTextBook method
#return A reference to a copy of this course's TextBook object.*/
public TextBook getTextBook(){return new TextBook(textBook);}
/**toString method
#return A string containing the course information.*/
public String toString(){
String str = courseNumber + " " + courseName+ "\n"+
instr+"\n" +
text;
return str;}}
And finally the TextBook class:
import java.text.*;
import java.util.*;
public class TextBook
{
DecimalFormat df = new DecimalFormat("$0.00");
private String title; // Title of the book
private String author; // Author's last name
private double price; // Wholesale cost of the book
public TextBook(String t, String a, double p){
title = t;
author = a;
price = p;}
public TextBook(TextBook object2){
title = object2.title;
author = object2.author;
price = object2.price;}
public void setTitle(String t){
title=t;}
public void setAuthor(String a){
author=a;}
public void setPrice(String p){
price=p;}
public void getTitle(){
return title;}
public void getAuthor(){
return author;}
public void getPrice(){
return price;}
public String toString(){
String str = "Required Textbook: \n" + " " + title+", " + author + ", " + df.format(price);
return str;}}
why does .setLastName() not work but .setName() does

In your class that has this
public void setLastName(String lname){
lastName=lname;
}
Make sure lastName exists as class variable. I am guessing this should be like:
private String lastName;
If you post your Course.java code, we all would be better equipped to explain what might be missing.