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How to Call a Method From Another Class, Through The Main Class?

Apologies for the poor title but I don't know how to phrase my issue. I am attempting to call the getSSN method from the Student class in my BubbleSorter class after a few students have been placed in an ArrayList. How can I call for the specific SSN variable. I understand why the error is occuring, but not how to change it to make it work. The error message is as follows: The method getSSN() is undefined for the type SearchandSort.
My Student Class:
public class Student {
private String firstName, lastName;
private int SSN;
public Student(String first, String last, int ssn) {
firstName = first;
lastName = last;
SSN = ssn;
}
public String toString() {
return lastName + ", " + firstName + " " + SSN + "\t";
}
public boolean equals(Object other) {
return (lastName.equals(((Student)other).getLastName()) && firstName.equals(((Student)other).getFirstName()) && (SSN == (((Student)other).getSSN())));
}
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 getSSN() {
return SSN;
}
public void setSSN(int SSN) {
this.SSN = SSN;
}
}
My BubbleSorter:
import java.lang.reflect.Array;
// “On my honor, I have neither received nor given any unauthorized assistance on this examination.”
public class BubbleSorter {
public static void bubbleSort(SortandSearch Students[]) {
int lastPos;
int index;
int temp;
for (lastPos = Students.length-1; lastPos >= 0; lastPos--) {
for (index = 0; index <= lastPos - 1; index++) {
if (((Students[index]).getSSN()) - ((Students[index+1].getSSN())) > 0) {
temp = Students[index].getSSN();
Students[index].getSSN() = Students[index+1].getSSN();
Students[index+1].getSSN() = temp;
}
}
}
}
}
My main class:
import java.util.ArrayList;
import java.util.Scanner;
public class SortandSearch {
public static void main(String[] args) {
Student a = new Student("Ryan", "Jones", 123456);
Student b = new Student("Jolie", "Decker", 123457);
ArrayList<Student> Students = new ArrayList<Student>();
Students.add(a);
Students.add(b);
System.out.println(Students);
bubbleSort(Students);
System.out.println(Students);
System.out.println("Please enter the SSN of the student you are searching for:");
Scanner scan = new Scanner(System.in);
int searchKey = scan.nextInt();
for (int index = 0; index < Students.size(); index++) {
if (Students.get(index).getSSN() == searchKey) {
System.out.print("The student with SSN " + searchKey + " is located at " + index);
}
}
}
}
EDIT:
The error now shows: The type of the expression must be an array type but it resolved to ArrayList.
New BubbleSorter:
import java.util.ArrayList;
// “On my honor, I have neither received nor given any unauthorized assistance on this examination.”
public class BubbleSorter {
public static void bubbleSort(ArrayList<Student> studentList) {
int lastPos;
int index;
int temp;
for (lastPos = studentList.size()-1; lastPos >= 0; lastPos--) {
for (index = 0; index <= lastPos - 1; index++) {
if ((studentList.get(index).getSSN()) - ((studentList.get(index).getSSN())) > 0) {
temp = studentList[index];
studentList[index] = studentList[index+1];
studentList[index+1] = temp;
}
}
}
}
}

There seem multiple things wrong to this code. I think you are trying unnessecary casting your arraylist to something else
First, I think your function signature should change to
public static void bubbleSort(ArrayList<Student> studentList)
And then you can access the elements with:
studentList.get(index).getSSN()

In SortandSearch you put instances of Student into ArrayList<>, and the your bubbleSort method must also take argument of this type or at least List and then convert it to array and return sorted list:
public static List<Student> bubbleSort(List<Student> studentsList) {
Student[] Students = studentsList.toArray(new Student[studentsList.size()]);
// ...
return Arrays.asList(Students);
}
And in the calling main method you need to store sorted list:
List<Student> sorted = BubbleSorter.bubbleSort(Students);
System.out.println(sorted);

how to get input for an array of class in java?

I am new in java and I trying to get information
for five students and save them into an array of classes. how can I do this?
I want to use class person for five students whit different informations
import java.io.IOException;
import java.util.*;
public class exam
{
public static void main(String[] args)
{
Scanner s = new Scanner(System.in);
// I want to get and save information in this array
person[] f = new student[5];
}
}
class person defined for get name and family name.
import java.util.*;
public abstract class person {
Scanner scr = new Scanner(System.in);
private String name , fname;
public void SetName() {
System.out.println("enter name and familyNAme :");
name = scr.next();
}
public String getname() {
return name;
}
public void setfname () {
System.out.println("enter familyname:");
fname = scr.next();
}
public String getfname() {
return fname;
}
}
class student that inherits from the class person for get studentID and student Scores .
import java.util.*;
class student extends person {
float[] p = new float[5];
int id , sum ;
float min;
public void inputs() {
System.out.println("enter the id :");
id = scr.nextInt();
}
public void sumation() {
System.out.println("enter points of student:");
sum= 0;
for(int i = 0 ; i<5 ; i++){
p[i]=scr.nextFloat();
sum+=p[i];
}
}
public void miangin() {
min = (float)sum/4;
}
}

So first things first, when creating Java objects, refrain from getting input inside the object so that if you decide to change the way you get input (e.g. transition from command line to GUI) you don't need to modify the Java object.
Second, getters and setters should only get or set. This would save some confusion when debugging since we don't have to check these methods/functions.
So here's the person object:
public abstract class Person {
protected String name, fname;
public Person (String name, String fname) {
this.name = name;
this.fname = fname;
}
public void setName (String name) {
this.name = name;
}
public String getName () {
return name;
}
public void setFname (String fname) {
this.fname = fname;
}
public String getFname () {
return fname;
}
}
And here's the student object (tip: you can make as much constructors as you want to make object creation easier for you):
public class Student extends Person {
private float[] p;
private int id;
public Student (String name, String fname) {
this (name, fname, -1, null);
}
public Student (String name, String fname, int id, float[] p) {
super (name, fname);
this.id = id;
this.p = p;
}
public void setP (float[] p) {
this.p = p;
}
public float[] getP () {
return p;
}
public void setId (int id) {
this.id = id;
}
public int getId () {
return id;
}
public float summation () {
float sum = 0;
for (int i = 0; i < p.length; i++)
sum += p[i];
return sum;
}
public float miangin () {
return summation () / 4.0f;
}
#Override
public String toString () {
return new StringBuilder ()
.append ("Name: ").append (name)
.append (" Family name: ").append (fname)
.append (" Id: ").append (id)
.append (" min: ").append (miangin ())
.toString ();
}
}
And lastly, wherever your main method is, that is where you should get input from. Take note that when you make an array, each index is initialized to null so you still need to instantiate each array index before using. I made a sample below but you can modify it depending on what you need.
import java.util.*;
public class Exam {
Scanner sc;
Person[] people;
Exam () {
sc = new Scanner (System.in);
people = new Person[5];
}
public void getInput () {
for (int i = 0; i < people.length; i++) {
System.out.print ("Enter name: ");
String name = sc.nextLine ();
System.out.print ("Enter family name: ");
String fname = sc.nextLine ();
System.out.print ("Enter id: ");
int id = sc.nextInt (); sc.nextLine ();
System.out.println ("Enter points: ");
float[] points = new float[5];
for (int j = 0; j < points.length; j++) {
System.out.printf ("[%d] ", j + 1);
points[j] = sc.nextFloat (); sc.nextLine ();
}
people[i] = new Student (name, fname, id, points);
}
}
public void printInput () {
for (Person p: people)
System.out.println (p);
}
public void run () {
getInput ();
printInput ();
}
public static void main (String[] args) {
new Exam ().run ();
}
}
Just one last tip, if you ever need dynamic arrays in Java, check out ArrayList.

You can add a class attribute, and then add class information for each student, or you can add a class class, define an array of students in the class class, and add an add student attribute, and you can add students to that class.

First of all, please write class names with capital letter (Student, Exam <...>).
Exam class:
import java.util.Scanner;
public class Exam {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
Student[] students = new Student[]{
new Student(),
new Student(),
new Student(),
new Student(),
new Student()
};
for (int i = 0; i < 5; i++) {
students[i].setFirstName();
students[i].setLastName();
students[i].setId();
}
}
}
Person class:
import java.util.Scanner;
public class Person {
String firstName, lastName;
public String getFirstName() {
return firstName;
}
public void setFirstName() {
System.out.println("Type firstName: ");
this.firstName = new Scanner(System.in).next();
}
public String getLastName() {
return lastName;
}
public void setLastName() {
System.out.println("Type lastName: ");
this.lastName = new Scanner(System.in).next();
}
}
Student class:
import java.util.Scanner;
public class Student extends Person{
int id;
public int getId() {
return id;
}
public void setId() {
//Converting String line into Integer by Integer.parseInt(String s)
System.out.println("Type id: ");
this.id = Integer.parseInt(new Scanner(System.in).next());
}
}

Collection object can't show output showing some undefined value in java, Arraylist, Collection

When I try to print a collection object, it prints Employee#122392Iie92. Why is it printing this and not the details of the employee list?
My code:
public class Employee {
private String name;
private String designation;
private int employeeId;
private int salary;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public int getEmployeeId() {
return employeeId;
}
public void setEmployeeId(int employeeId) {
this.employeeId = employeeId;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
}
import java.util.ArrayList;
import java.util.Scanner;
public class EmployeeManagement {
static Scanner sc = new Scanner(System.in);
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList <Employee> lst = new ArrayList <Employee> ();
System.out.println("Enter the number of employees : ");
int num = sc.nextInt();
EmployeeManagement emp = new EmployeeManagement();
emp.addEmployeeName( num, lst);
}
public void addEmployeeName(int num,ArrayList<Employee> lst) {
Employee em = new Employee();
for(int i =0; i<num ; i++)
{
System.out.println("Enter the employee id : ");
em.setEmployeeId(sc.nextInt());
System.out.println("Enter the name of employee : ");
em.setName(sc.next());
System.out.println("Enter the designation of employee : ");
em.setDesignation(sc.next());
System.out.println("Enter the Salary of employees : ");
em.setSalary(sc.nextInt());
lst.add(em);
}
System.out.println(lst);
}
}

It is printing using the default toString method of the Object class. You need to override toString in the Employee class if you want to show values. It is currently showing the class name and hashcode.
Write a toString method like this in Employee:
#Override
public String toString(){
SubString sb = new SubString();
sb.append("Name :- ")append(name).append(id); //all relevant fields
return sb.toString();
}
Move new statement inside loop else you are adding and updating same object again and again.
public void addEmployeeName(int num,ArrayList<Employee> lst) {
for(int i =0; i<num ; i++)
{
Employee em = new Employee();
System.out.println("Enter the employee id : ");
em.setEmployeeId(sc.nextInt());
System.out.println("Enter the name of employee : ");
em.setName(sc.next());
System.out.println("Enter the designation of employee : ");
em.setDesignation(sc.next());
System.out.println("Enter the Salary of employees : ");
em.setSalary(sc.nextInt());
lst.add(em);
}
System.out.println(lst);
}
}

String ArrayList returning null values

I am new to java and doing some arraylist work, and when compiling my lists just return null values instead of names I have typed in.
I don't understand why this is so, so if anyone could advise/help me that would be great.
Here is my main code
import java.util.*;
public class StudentData
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
ArrayList<Student> studentList = new ArrayList<Student>();
String yesNo = "true";
do
{
System.out.println("Enter student's name: ");
String name = in.next();
Student s = new Student();
studentList.add(s);
String input;
do
{
System.out.println("Would you like to enter data for another student? Yes/No ");
yesNo = in.next();
}
while (!yesNo.equalsIgnoreCase("YES") && !yesNo.equalsIgnoreCase("NO"));
}
while (yesNo.equalsIgnoreCase("YES"));
for(int i = 0; i < studentList.size(); i++)
{
System.out.println(studentList.get(i).getName());
}
}
}
And
class Student
{
private String studentName;
public StudentData(String name)
{
setName(name);
}
public String getName()
{
return studentName;
}
public void setName(String name)
{
studentName = name;
}
}

You're creating a student but didn't set the name :
String name = in.next();
Student s = new Student();
studentList.add(s);
Try with :
String name = in.next();
Student s = new Student();
s.setName(name);
studentList.add(s);
Also replace your constructor. I.e :
public StudentData(String name){
setName(name);
}
should be
public Student(String name) {
setName(name);
}
Then you will be able to do Student s = new Student(name);

Class Constructor Problems While Doing A Linear Search Across Two Classes

Im creating a program that is supposed have the user enter a student name and see if it exist in the student array using a linear search method. The student array is in a different class and im having trouble creating a constructor i have tried many things and its not working can someone point me in the right direction.
My linear search class is
import java.util.*;
import java.util.Scanner;
public class LinearSearch {
public int find(Student [] a, String nm) {
for (int i = 0; i < a.length; i++) {
if (a[i].equals(nm)){
return i;
break;
}
else{
return -1;
}
}
}
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
LinearSearch search = new LinearSearch();
Student stu = new Student();
Student [] arr = stu.getArray();
System.out.print("Enter the name to search: ");
String name = reader.nextLine();
int n = search.find(arr, name);
if ((n >= 0) && (n < arr.length)) {
System.out.println(name + " was found at index: " + n);
} else {
System.out.println(name + " was not found");
}
}
}
My Student class is
import java.util.*;
public class Student {
public Student(){
}
public Student [] getArray(){
Student [] studentArray = new Student[3];
studentArray[0] = new Student ("Mel");
studentArray[1] = new Student ("Jared");
studentArray[2] = new Student ("Mikey");
return studentArray;
}
}

You defined a constructor with no argument:
public Student() {
}
But you're invoking a constructor which needs a String as argument:
studentArray[0] = new Student("Mel");
So, your constructor should have a String as argument:
public Student(String name)
And you should probably store this name as a field in the Student class:
private String name;
public Student(String name) {
this.name = name;
}
Note that there is no way that a Student instance could be equal to a String instance. You should provide a getter method for the name, and compare the entered String with the name of the student, instead of comparing it with the student itself.

import java.util.*;
public class Student {
private String name;
public Student(String name){
this.name = name;
}
public Student [] getArray(){
Student [] studentArray = new Student[3];
studentArray[0] = new Student ("Mel");
studentArray[1] = new Student ("Jared");
studentArray[2] = new Student ("Mikey");
return studentArray;
}
public String getName(){
return name;
}
}
and of course in the compersion you'll need to do:
f (a[i].getName().equals(nm)){

public class Student {
private String studentName;
private Student[] studentArray;
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
public Student[] getStudentArray() {
return studentArray;
}
public void setStudentArray(Student[] studentArray) {
this.studentArray = studentArray;
}
public Student(){
studentArray = new Student[3];
}
public Student[] getArray() {
Student st1 = new Student();
st1.setStudentName("mel");
Student st2 = new Student();
st2.setStudentName("Jared");
Student st3 = new Student();
st3.setStudentName("Mikey");
studentArray[0]=st1;
studentArray[1]=st2;
studentArray[2]=st3;
return studentArray;
}
}
the above code is your Student class. there is no need to create a constructor though. but because you would like it i put it in the code.
the LinearSearch class is as follow:
public class LinearSearch {
private int i;
public int find(Student[] a, String nm) {
for ( i = 0; i < a.length; i++) {
if (a[i].getStudentName().equals(nm)) {
break;
} else {
i = -1;
}
}
return i;
}
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
LinearSearch search = new LinearSearch();
Student stu = new Student();
Student[] arr = stu.getArray();
System.out.print("Enter the name to search: ");
String name = reader.nextLine();
int n = search.find(arr, name);
if ((n >= 0) && (n < arr.length)) {
System.out.println(name + " was found at index: " + n);
} else {
System.out.println(name + " was not found");
}
}
}