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Cannot find symbol - class InventoryItem

I re-type these code from a book and somehow I got error " Cannot find symbol - class InventoryItem "
import java.util.Scanner;
public class ReturnObject {
public static void main(String[] args) {
InventoryItem item;
item = getData();
System.out.println("Des: " + item.getDescription() + " Unit: " +
item.Units());
}
public static InventoryItem getData() {
String desc;
int units;
Scanner keyboard = new Scanner(System.in);
System.out.print("enter descri: ");
desc = keyboard.nextLine();
System.out.print("number of unit: ");
units = keyboard.nextInt();
return new InventoryItem(desc, units);
}
}
I'm new to java please help
thank you.

I think this should be the InventoryItem you need.
/**
* This class uses three constructors.
*/
public class InventoryItem {
private String description; // Item description
private int units; // Units on-hand
/**
* No-arg constructor
*/
public InventoryItem() {
description = "";
units = 0;
}
/**
* The following constructor accepts a
* String argument that is assigned to the
* description field.
*/
public InventoryItem(String d) {
description = d;
units = 0;
}
/**
* The following constructor accepts a
* String argument that is assigned to the
* description field, and an int argument
* that is assigned to the units field.
*/
public InventoryItem(String d, int u) {
description = d;
units = u;
}
/**
* The setDescription method assigns its
* argument to the description field.
*/
public void setDescription(String d) {
description = d;
}
/**
* The setUnits method assigns its argument
* to the units field.
*/
public void setUnits(int u) {
units = u;
}
/**
* The getDescription method returns the
* value in the description field.
*/
public String getDescription() {
return description;
}
/**
* The getUnits method returns the value in
* the units field.
*/
public int getUnits() {
return units;
}
}
complete example click here and here

The class you are currently in cannot find the class (symbol) InventoryItem. You need to define this class & the getData method.
public class InventoryItem{
private String desc;
private int units;
public InventoryItem(){
Scanner keyboard = new Scanner(System.in);
System.out.print("enter descri: ");
desc = keyboard.nextLine();
System.out.print("number of unit: ");
units = keyboard.nextInt();
}
public static InventoryItem getData() {
return this;
}
}

maybe your InventoryItemclass:
public class InventoryItem {
private String desc;
private int units;
public InventoryItem(String desc, int units) {
this.desc=desc;
this.units=units;
}
public String getDescription() {
return desc;
}
public int Units() {
return units;
}
}

Why is the student counter skipping a number

I am trying to build a program which counts each student from 1 - 10. But the output seems to skip 5 after 4 and go straight to 6.
The output I get is:
MathStudent[1]-Smith: - Count:1
MathStudent[2]-Jack: - Count:1
MathStudent[3]-Victor: - Count:1
MathStudent[4]-Mike: - Count:1
Science Student[6]-Dave: - Count:1
Science Student[7]-Oscar: - Count:1
Science Student[8]-Peter: - Count:1
Computer Student[9] Philip: - Count:1
Computer Student[10] Shaun: - Count:1
Computer Student[11] Scott: - Count:1
Main class:
public class JavaLab5 {
public static final int DEBUG = 0;
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
StudentThread studentThread = new StudentThread();
studentThread.start();
}
}
Student class:
public class Student {
static int studentCounter = 1;
String name;
private int count = 0;
public static int instances = 0;
// Getters
public String getName() {
return this.name;
}
// Setters
public void setName(String name) {
if (JavaLab5.DEBUG > 3) System.out.println("In Student.setName. Name = "+ name);
this.name = name;
}
/**
* Default constructor. Populates name,age and gender
* with defaults
*/
public Student() {
instances++;
this.name = "Not Set";
}
/**
* Constructor with parameters
* #param name String with the name
*/
public Student(String name) {
this.name = name;
}
/**
* Destructor
* #throws Throwable
*/
protected void finalize() throws Throwable {
//do finalization here
instances--;
super.finalize(); //not necessary if extending Object.
}
/**
*
*/
public void getCounter() {
for (int j = 0; j < 1; j++) {
count++;
System.out.println(count);
}
}
#Override
public String toString () {
return this.name;
}
public String getSubjects() {
return this.getSubjects();
}
}
ComputerStudent class:
public class ComputerStudent extends Student {
int studCountObj;
/**
* Default constructor
* #fortanGrade
* #adaGrade
*/
public ComputerStudent() {
super();
}
public ComputerStudent(String name) {
super(name);
studentCounter++;
studCountObj=studentCounter;
}
/**
* Display information about the subject
* #return
*/
#Override
public String getSubjects(){
return(" Computer Student" + "[" + studCountObj + "] " + name + ": ");
}
}
MathStudent class:
public class MathStudent extends Student {
int studCountObj;
/**
* Default constructor
* #param name
*/
public MathStudent(String name) {
super(name);
studCountObj=studentCounter;
studentCounter++;
}
public MathStudent() {
super();
}
/**
* Display information about the subject
* #return
*/
#Override
public String getSubjects(){
return(" MathStudent" + "[" + studCountObj + "]" + "-" + name + ": ");
}
}
ScienceStudent class:
public class ScienceStudent extends Student {
int studCountObj;
/**
* Default constructor
*/
public ScienceStudent() {
super();
}
public ScienceStudent(String name) {
super(name);
studentCounter++;
studCountObj=studentCounter;
}
/**
* Display information about the subject
* #return
*/
#Override
public String getSubjects(){
return(" Science Student" + "[" + studCountObj + "]" + "-" + name + ": ");
}
}
StudentThread class:
public class StudentThread extends Thread {
public void run(){
Student s[] = new Student[10];
s[0] = new MathStudent("Smith");
s[1] = new MathStudent("Jack");
s[2] = new MathStudent("Victor");
s[3] = new MathStudent("Mike");
s[4] = new ScienceStudent("Dave");
s[5] = new ScienceStudent("Oscar");
s[6] = new ScienceStudent("Peter");
s[7] = new ComputerStudent("Philip");
s[8] = new ComputerStudent("Shaun");
s[9] = new ComputerStudent("Scott");
for (int j = 0; j < 10; j++) {
for (Student item : s) {
System.out.print(item.getSubjects() + " - " + "Count:");
item.getCounter();
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
}
}
}
}
My question is why is the output skipping 5?

In Science Class:
super(name);
studentCounter++;
studCountObj=studentCounter;
You first increase the studentCounter from 5 to 6 and then assign it to studCountObj. Swap that would print 5.

You have to change this:
MathStudent class:
public class MathStudent extends Student {
int studCountObj;
/**
* Default constructor
* #param name
*/
public MathStudent(String name) {
super(name);
studentCounter++; //First this
studCountObj=studentCounter; //Then this
}
public MathStudent() {
super();
}
/**
* Display information about the subject
* #return
*/
#Override
public String getSubjects(){
return(" MathStudent" + "[" + studCountObj + "]" + "-" + name + ": ");
}
}
And this:
Student class:
public class Student {
static int studentCounter = 0; //Start with zero
String name;
private int count = 0;
public static int instances = 0;
// Getters
public String getName() {
return this.name;
}
// Setters
public void setName(String name) {
if (JavaLab5.DEBUG > 3) System.out.println("In Student.setName. Name = "+ name);
this.name = name;
}
/**
* Default constructor. Populates name,age and gender
* with defaults
*/
public Student() {
instances++;
this.name = "Not Set";
}
/**
* Constructor with parameters
* #param name String with the name
*/
public Student(String name) {
this.name = name;
}
/**
* Destructor
* #throws Throwable
*/
protected void finalize() throws Throwable {
//do finalization here
instances--;
super.finalize(); //not necessary if extending Object.
}
/**
*
*/
public void getCounter() {
for (int j = 0; j < 1; j++) {
count++;
System.out.println(count);
}
}
#Override
public String toString () {
return this.name;
}
public String getSubjects() {
return this.getSubjects();
}
}
In the ScienceStudent class and in the Computer student class you already do this, so when you change this pattern in the Mathstudent class you will get your first output, because when the thread goes to ScienceStudent it will add the number 1 again, you skip a number then.

How to add multiple students to student class?

Im trying to create a student class, a course class and the main class. I am trying to add students to the course, and when students are added to the class the number of students in the course should increase, when the the code is run it should print the course details followed by the students in the course.
I have got the following code:
Main class:
public class JavaLecture3 {
public static final int DEBUG = 0;
public static void main(String [] args){
//Student student = new Student(); // Calling default constructor here.
Course course = new Course();
student = new Student(21, "Joe", "CSE", "07447832342");
course = new Course("CSE", "Tom", 5);
System.out.println("Course Information: ");
System.out.println("-------------------");
System.out.println(course);
System.out.println();
System.out.println("Student contains: "); // calls student.toString());
System.out.println("-------------------");
System.out.println(student);
}
}
Course class:
public class Course {
ArrayList<Student> studentList;
private String courseName;
private String teacher;
private int noOfStudents;
//Getters
public String getCourseName(){
return this.courseName;
}
public int getNoOfStudents(){
return this.noOfStudents;
}
public String getTeacher(){
return this.teacher;
}
//Setters
public void setCourseName(String courseName){
this.courseName = courseName;
}
public void setNoOfStudents(int noOfStudents){
this.noOfStudents = noOfStudents;
}
public void setTeacher(String teacher){
this.teacher = teacher;
}
/**
* Default constructor. Populates course name, number of students with defaults
*
*/
public Course(){
this.noOfStudents = 0;
this.courseName = "Not Set";
this.teacher = "Not Set";
studentList = new ArrayList<Student>();
}
/**
* Constructor with parameters
* #param noOfStudents integer
* #param courseName String with the Course name
* #param teacher String with the teacher
*/
public Course(String courseName, String teacher, int noOfStudents){
this.courseName = courseName;
this.teacher = teacher;
noOfStudents = noOfStudents;
studentList = new ArrayList<Student>();
}
public static void addStudent(Student newStudent){
if(studentList.size()==noOfStudents){
System.out.println("The class is full, you cannot enrol.");
}
else {
studentList.add(newStudent);
}
}
public String toString() {
return "Course Name: " + this.courseName + " Teacher: " + this.teacher
+ " Number of Students: " + this.noOfStudents;
}
}
Student class:
public class Student {
private String name;
private int age;
public String gender = "na";
private String course;
private String phoneNo;
public static int instances = 0;
// Getters
public int getAge(){
return this.age;
}
public String getName(){
return this.name;
}
public String getCourse(){
return this.course;
}
public String getPhoneNo(){
return this.phoneNo;
}
// Setters
public void setAge(int age){
this.age = age;
}
public void setName(String name){
if (JavaLecture3.DEBUG > 3) System.out.println("In Student.setName. Name = "+ name);
this.name = name;
}
public void setCourse(String course){
this.course = course;
}
public void setPhoneNo(String phoneNo){
this.phoneNo = phoneNo;
}
/**
* Default constructor. Populates name,age,gender,course and phone Number
* with defaults
*/
public Student(){
instances++;
this.age = 18;
this.name = "Not Set";
this.gender = "Not Set";
this.course = "Not Set";
this.phoneNo = "Not Set";
}
/**
* Constructor with parameters
* #param age integer
* #param name String with the name
* #param course String with course name
* #param phoneNo String with phone number
*/
public Student(int age, String name, String course, String phoneNo){
this.age = age;
this.name = name;
this.course = course;
this.phoneNo = phoneNo;
}
/**
* Gender constructor
* #param gender
*/
public Student(String gender){
this(); // Must be the first line!
this.gender = gender;
}
protected void finalize() throws Throwable{
//do finalization here
instances--;
super.finalize(); //not necessary if extending Object.
}
public String toString (){
return "Name: " + this.name + " Age: " + this.age + " Gender: "
+ this.gender + " Course: " + this.course + " Phone number: "
+ this.phoneNo;
}
}

Reference:
http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html?is-external=true
Course.getNoOfStudents should just return studentList.size(). No need to maintain a separate variable.
To print a list of students (from Course):
for(int i=0;i<studentList.size();i++) System.out.println(studentList.get(i));

Since you initialized the array list in the Course class, you should add the students to it. You should create a method in Course that adds an object to the array list such as:
public void addStudent(Student s){
studentList.add(s);
noOfStudents++;
}
To add multiple students:
public void addStudents(Student[] students){
for(int i = 0; i < students.length; i++){
studentList.add(students[i]);
}
}
You're almost there, just use the .add method made for you in the array list.

public class JavaLecture3 {
public static final int DEBUG = 0;
public static void main(String [] args){
Student student = new Student(); // Calling default constructor here.
Course course = new Course();
student = new Student(21, "Joe", "CSE", "07447832342");
course = new Course("CSE", "Tom", 5);
course.addStudent(student);
System.out.println("Course Information: ");
System.out.println("-------------------");
System.out.println(course);
System.out.println();
System.out.println("Student contains: "); // calls student.toString());
System.out.println("-------------------");
System.out.println(student);
}
}
public class Course {
List<Student> studentList;
private String courseName;
private String teacher;
private int noOfStudents;
// Getters
public String getCourseName() {
return this.courseName;
}
public int getNoOfStudents() {
return this.noOfStudents;
}
public String getTeacher() {
return this.teacher;
}
// Setters
public void setCourseName(String courseName) {
this.courseName = courseName;
}
public void setNoOfStudents(int noOfStudents) {
this.noOfStudents = noOfStudents;
}
public void setTeacher(String teacher) {
this.teacher = teacher;
}
/**
* Default constructor. Populates course name, number of students with
* defaults
*
*/
public Course() {
this.noOfStudents = 0;
this.courseName = "Not Set";
this.teacher = "Not Set";
studentList = new ArrayList<Student>();
}
/**
* Constructor with parameters
*
* #param noOfStudents
* integer
* #param courseName
* String with the Course name
* #param teacher
* String with the teacher
*/
public Course(String courseName, String teacher, int noOfStudents) {
this.courseName = courseName;
this.teacher = teacher;
this.noOfStudents = noOfStudents;
studentList = new ArrayList<Student>();
}
public void addStudent(Student newStudent) {
if (studentList.size() == noOfStudents) {
System.out.println("The class is full, you cannot enrol.");
} else {
studentList.add(newStudent);
}
}
#Override
public String toString() {
return "Course Name: " + this.courseName + " Teacher: " + this.teacher
+ " Number of Students: " + studentList.size();
}
}
public class Student {
private String name;
private int age;
public String gender = "na";
private String course;
private String phoneNo;
public static int instances = 0;
// Getters
public int getAge() {
return this.age;
}
public String getName() {
return this.name;
}
public String getCourse() {
return this.course;
}
public String getPhoneNo() {
return this.phoneNo;
}
// Setters
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
if (JavaLecture3.DEBUG > 3)
System.out.println("In Student.setName. Name = " + name);
this.name = name;
}
public void setCourse(String course) {
this.course = course;
}
public void setPhoneNo(String phoneNo) {
this.phoneNo = phoneNo;
}
/**
* Default constructor. Populates name,age,gender,course and phone Number
* with defaults
*/
public Student() {
instances++;
this.age = 18;
this.name = "Not Set";
this.gender = "Not Set";
this.course = "Not Set";
this.phoneNo = "Not Set";
}
/**
* Constructor with parameters
*
* #param age
* integer
* #param name
* String with the name
* #param course
* String with course name
* #param phoneNo
* String with phone number
*/
public Student(int age, String name, String course, String phoneNo) {
this.age = age;
this.name = name;
this.course = course;
this.phoneNo = phoneNo;
}
/**
* Gender constructor
*
* #param gender
*/
public Student(String gender) {
this(); // Must be the first line!
this.gender = gender;
}
protected void finalize() throws Throwable {
// do finalization here
instances--;
super.finalize(); // not necessary if extending Object.
}
public String toString() {
return "Name: " + this.name + " Age: " + this.age + " Gender: "
+ this.gender + " Course: " + this.course + " Phone number: "
+ this.phoneNo;
}
}

public class JavaLecture3 {
public static final int DEBUG = 0;
public static void main(String [] args){
//Create course object
Course course = new Course("CSE", "Tom", 5);
Scanner scanner = new Scanner(System.in);
String cmd = "Yes";
while(cmd.equals("Yes")){
Student student = new Student();
System.out.print("Enter a new student? ");
cmd = scanner.next();
if (cmd.equals("Yes")){
//Read student name
System.out.print("Enter a student name: ");
String name = scanner.next();
student.setName(name);
//Read student Age
System.out.print("Enter a student age: ");
int age = scanner.nextInt();
student.setAge(age);
//Read student Course
System.out.print("Enter a student course: ");
String stdent_course = scanner.next();
student.setCourse(stdent_course);
//register the student to the class
course.addStudent(student);
}
}
scanner.close();
System.out.println("Course Information: ");
System.out.println("-------------------");
System.out.println(course.toString());
System.out.println();
}
}
I reworked a bit your toString() method from Course class. This should print the list of students attending a class.
public String toString (){
String ret_value = "Name: " + this.name + " Age: " + this.age + " Gender: "
+ this.gender + " Course: " + this.course + " Phone number: "
+ this.phoneNo + " Students attending this course:";
for (Student student: studentList) {
ret_value = ret_value + " " + Student.getName();
}
return ret_value;
}

How can I implement Random in java

Well, I need to implement two classes Student and School. Each student has an Id number consisting of number of arrival and the dormitory number, the second one should be random number from an array of elements.
Then I need to register these students to appropriate schools, there are four of them. This registration have to be random also. so I have Student and Schools classes here,
public class Student {
private String name;
private int id, size;
private int dorm;
/**
* Constructor of a class Student
*
* #param n sets the name of the student
*/
public Student(String n) {
name = n;
int d[] = {11, 19, 20, 22, 23, 24, 38, 39};
Random r = new Random();
dorm = d[r.nextInt(d.length)];
}
/**
* #return the name
*/
public String getName() {
return name;
}
/**
* #param name the name to set
*/
public void setName(String name) {
this.name = name;
}
/**
* #return the dorm
*/
public int getDorm() {
return dorm;
}
/**
* the id to set
*/
public void setId() {
id = size;
id = id*100 + dorm;
}
/**
* #return the id
*/
public int getId() {
return id;
}
#Override
public String toString() {
String result = "The student " + name + " has an id " + id + ". Located in the dormitory #" + dorm + ".";
return result;
}
And School class here,
import adt.Queue;
public class School {
private int size;
private String name;
private Queue q = new LinkedListQueue();
public School(String n) {
name = n;
size = 0;
}
public void register(Student st) {
q.enqueue(st);
size++;
}
public int getSize() {
return size;
}
public void viewStudents() {
System.out.println(q.toString());
}
#Override
public String toString() {
String str = "The School of " + name + ". The number of students is " + size + ".";
return str;
}
So as you can see, I have register method in the School class which register new Student to a specific school.
So my problem is that how can I get data size from a School class to use it in the Student class ???
I am only a student don't judge me please ^^)

When you add a student to the school, you should also tell the student what school they're in.
Add a field and a method to Student
public class Student {
private String name;
private int id, size;
private int dorm;
private School school;
public void setSchool( School school ) {
this.school = school;
}
Then add the code in School to tell the student.
public void register(Student st) {
q.enqueue(st);
size++;
st.setSchool( this );
}
Now as long as school is not null in Student, a student can find the size of their school.

If I understand your problem correctly, what you need is to add an int parameter to your student's setId() method:
public void setId(int id) {
this.id = id * 100 + dorm;
}
and then on the register() method you would do:
public void register(Student st) {
q.enqueue(st);
st.setId(size++);
}
I hope that helps you, good luck!

i have trouble with printing an array after reading it in JAVA

i have problem with printing the array after reading it. After printing, the address of memory is printed, not value of the array. What can i do for that ?
public class MyClass
{
Student St = new Student();
Student[]Array1 = new Student[10];
void AddList()
{
Scanner Scan = new Scanner(System.in);
for (int i=0; i<Array1.length & i<ArrayF1.length; i++)
{
System.out.println("Enter Student NAME Number " + (i+1) + ":");
Array1[i] = new Student();
Array1[i].setName(Scan.next());
//System.out.println("Enter Student MARK Number " + (i+1) + ":");
//St.setMark(Scan.nextFloat());
}
}
this is my print method. The result of print is like this
(studentproject.Student#1a758cb)
void PrintList()
{
for (int i=0; i<Array1.length; i++)
{
System.out.println(Array1[i]);
}
}
this is my Student Class that i have all my setter and getter method on that ... So i have 3 Class how can i work with this 3 class and in one of them get the data and in another print the Mark data and in third class print the Student Name data ... how can i do that ... i do some code but i dont know is it correct or not ... thanks for your help ...
public class Student
{
private String Name;
private float Mark;
/**
* #return the Name
*/
public String getName() {
return Name;
}
/**
* #param Name the Name to set
*/
public void setName(String Name) {
this.Name = Name;
}
/**
* #return the Mark
*/
public float getMark() {
return Mark;
}
/**
* #param Mark the Mark to set
*/
public void setMark(float Mark) {
this.Mark = Mark;
}
}

Just override the toString() method in Student class, and return the appropriate string you want to get printed when you print an instance.
It may look like: -
#Override
public String toString() {
return "Name: " + studentName;
}
Currently, the default implementation of toString() method of Object class is invoked, and what you are seeing is the format returned from that method, which is of the form - Type#hashCode

Here I've added some stuff how toString() method can be override
public class Student {
private String name;
private int id;
float mark;
public Student() {
}
public Student(String name, int id) {
this.name = name;
this.id = id;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getMark() {
return mark;
}
public void setMark(float mark) {
this.mark = mark;
}
#Override
public String toString() {
return "Student[ID:" + id + ",Name:" + name + ",Mark:"+mark+"]";
}
public void printStudentInfo() {
// print all the details of student
}
public static void main(String[] args) {
Student[] students = new Student[10];
Scanner scanner = new Scanner(System.in);
for (int i = 0; i < students.length; i++) {
System.out.println("Enter Student Name " + (i + 1) + ":");
String name = scanner.nextLine();
Student student = new Student(name, i + 1);
System.out.println("Enter Student MARK Number " + (i + 1) + ":");
float mark = scanner.nextFloat();
student.setMark(mark);
students[i]=student;
}
for(Student student:students) {
// by default toStirng method is called
System.out.println(student);
//or you can call like
//student.printStudentInfo();
}
}
}