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Constructors and methods in java

I want to create the below class
associatename:String
workstatus:String
associate() :constructor
getassociatename():String
setassociatename(String):void
getworkstatus()String
tracksassociatestatus():int
setworkstatus(String):void
The trackAssociateStatus method takes the number of days as argument and sets the work status of the associate based on the number of days. The first 20 days they learn “C”, the next 20 days they learn “Java” In the Main class invoke the trackAssociateStatus method and find the work status and display the output.
output:The associate abc work status:Project phase
I tried this....But i got error
//associate class
public class associate{
private int associatename;
private String workstatus;
private int days;
void associate()
{
getassociatename();
setassociatename();
getworkstatus();
tracksassociatestatus();
setworkstatus();
}
public int getassociatename()
{
return associatename;
}
public void setassociatename(int associatename)
{
this.associatename=associatename;
}
public String getworkstatus()
{
return workstatus;
}
public void tracksassociatestatus(int days)
{
if(days<20)
setworkstatus("C");
else
setworkstatus("Java");
}
public void setworkstatus(String workstatus)
{
this.workstatus=workstatus;
}
}
//main class
associate a =new associate();
Scanner in=new Scanner(System.in);
int associateid=0;
String workstatus=null;
int days=0;
System.out.println("Enter the associateid:");
associateid=in.nextInt();
a.associateid=(associateid);
System.out.println("Enter the no of days:");
days=in.nextInt();
a.trackassociatestatus();
System.out.println("The id is "+a.getassocaiteid()+" work status "+a.getworkstatus());

Based on your (seemingly) UML spec, your class would look like the following:
public class Associate {
private String associateName;
private String workStatus;
public Associate() {
// This constructor is optional, a no-args constructor is added by the compiler to any class not explicitly naming a constructor.
}
public String getAssociateName() {
return associateName;
}
public void setAssociateName(String associateName) {
this.associateName = associateName;
}
public String getWorkStatus() {
return workStatus;
}
public void setWorkStatus(String workStatus) {
this.workStatus = workStatus;
}
public int tracksAssociateStatus() {
// TODO write logic here
return 1; // TODO change to whatever you need to return
}
}
You were specifying int for getAssociateName, when associateName is a String. This won't work; you need your getter return type to be the same as your field data type, or you need to convert the data to the method's return type. (The former is best practice).
Constructors don't specify a type, the class name is used and the compiler will understand what you want to do (which is return a new instance of the class). Therefore, your void associate() will tell the compiler "create a method called associate that doesn't return anything".

Well, would be nice if you provide the error itself for us.
But meanwhile, have you notice that your tracksassociatestatus method recieves an integer parameter days, and your constructor passes nothing to it?
So try changing your constructor to be something like:
Public associate() {
getassociatename();
setassociatename();
getworkstatus();
tracksassociatestatus(10);
setworkstatus();
}
For a cleaner code, check the other answer.
If you still have errors, please share them.

import java.util.*;
public class Associate
{
private String associateName;
private int workStatus;
private int days;
Scanner sc = new Scanner(System.in);
public String getAssociateName()
{
System.out.println("Enter the Associate id:");
associateName = sc.nextLine();
return associateName;
}
public void setassociatename(int associatename)
{
this.associateName=associateName;
}
public String tracksAssociatename()
{
return associateName;
}
public int getWorkStatus()
{
System.out.println("Enter the number of days");
days = sc.nextInt();
return days;
}
public void setWorkStatus(String workStatus)
{
this.workStatus=workStatus;
}
enter code here
public `enter code here`int tracksAssociateStatus()
{
return days;
}
public static void main(String args[])
{
Associate obj = new Associate();
obj.getAssociateName();
obj.getworkstatus();
System.out.println("The Associate name "+obj.tracksAssociatename()+" work Status "+obj.tracksAssociateStatus());
}
}

Instantiate array of objects with a variable

I wrote some classes in Java but when I run the program I receive the error "ArrayIndexOutOfBoundsException", the incriminate class is this:
public class Bank {
private String name;
private int maxbankaccount;
private int activebankaccount;
private String radice = "IT8634";
private Conto[] bankaccount = new Conto[maxbankaccount];
public void addconto(String cf) {
bankaccount[activebankaccount] = new Conto(radice + activebankaccount , cf);
activebankaccount++;
}
public Bank(String name, int maxbankaccount) {
this.name = name;
this.maxbankaccount = maxbankaccount;
}
}
I wrote a tester class to test :
public class TestBank {
public static void main (String[] args) {
Bank b1 = new Bank("Fidelity", 10);
b1.addconto("PROVA");
}
}
Since I didn't seem to have made logical errors using the array I debugged, I realized that in the creation of the array of objects the maxbankaccount variable isn't 10 (value passed in Test) but as default value (0),then I tried passing 10 directly and it works good. Why is not the value 10 of maxbankaccount passed but 0?

private Conto[] bankaccount = new Conto[maxbankaccount];
This initialization takes place before the rest of the constructor runs.
Move it into the constructor:
public Bank(String name, int maxbankaccount) {
this.name = name;
this.maxbankaccount = maxbankaccount;
this.bankaccount = new Conto[maxbankaccount];
}

You have indeed made a logical error. The array bankaccount is getting initialized when the class is instantiated and is always 0.
Move it into the constructor and initialize it.
public Bank(String name, int maxbankaccount) {
/* ... */
this.bankaccount = new Conto[maxbankaccount];
}

Further more than the issues that are in the other answers, this
private int activebankaccount;
does not initialize the variable activebankaccount
So in:
public void addconto(String cf) {
bankaccount[activebankaccount] = new Conto(radice + activebankaccount , cf);
activebankaccount++;
}
you are using an uninitialized vale as index of the array bankaccount

Check if class has a variable in its constructor based on a string?

Let's say I have a class named Person and its constructor had variables like name, age, hairColor and so on. If I had a function that receives a string that should match one of the class's variables, how could I check if that class actually had that variable and how could I go about modifying it? For example:
public class Person {
public String name;
public int age;
public String hairColor;
public Person() {
name = "Bryce";
age = 21;
hairColor = "brown";
}
public void changeHairColor(String variable, String color) {
if (/*this class contains the variable passed as an argument to this method*/) {
// Person[variable] = color
}
}
}
I'm a python dev, mostly, so the method changeHairColor has some pseudo-python in it. I want to be able to edit the variable in a similar way you could edit variables inside of dictionaries with Python:
person = {
"name": "Bryce",
"age": 21,
"hairColor": "brown"
}
def changeHairColor(variable, color):
person[variable] = color
If that is at all possible.

The only way to do it in Java is to use Java Reflection API:
public class Test {
public String name;
public int age;
public String hairColor;
public void setProperty(String property, Object value) {
try {
Field declaredField = this.getClass().getDeclaredField(property);
switch (declaredField.getAnnotatedType().getType().getTypeName()) {
case "java.lang.String":
declaredField.set(this, value);
break;
// handle other types
}
} catch (NoSuchFieldException e) {
// handle exception
} catch (IllegalAccessException e) {
// handle exception
}
}
public static void main(String[] args) {
Test test = new Test();
test.setProperty("name", "Bob");
System.out.println(test.name);
}
}

I would not solve this with reflection. If your PlayerCharacter has an enumerable set of attributes, I would model these as a Java enum and store the attribute values within the PlayerCharacter object in an EnumMap:
import java.util.EnumMap;
public class PlayerCharacter {
public enum Attribute {
AGILITY,
DEXTERITY,
/* etc ...*/
VITALITY
}
private EnumMap<Attribute, Integer> attributes = new EnumMap<>(Attribute.class);
public PlayerCharacter() {
// initialize each attribute with a default value (0 in this example)
for (Attribute a : Attribute.values()) {
attributes.put(a, new Integer(0));
}
}
public int getValue(Attribute attribute) {
return attributes.get(attribute);
}
public void levelUp(Attribute attribute, int amount) {
attributes.put(attribute, attributes.get(attribute) + amount);
}
}
The biggest benefit of using an enum instead of plain old String (+reflection), is that this way you get compile-time type safety for the code that's using your PlayerCharacter.

Using Reflection API, you can access the methods and properties on an object at run time. The other answer describes its usage. But I don't recommend reflections for your problem. How about the following:
public void changeHairColor(String variable, String color) {
if("name".equalsIgnoreCase(variable))
this.name = color;
else if("age".equalsIgnoreCase(variable))
this.age = Integer.parseInt(color);
else if("color".equalsIgnoreCase(variable))
this.color = color;
else
throw new Exception ("error - property not available");
}
}
Note, your existing method name 'changeHairColor' doesn't make sense in the context. It should be someething like 'changeProperty' because you are not just changing the 'color', you are changing any available property with this method.

How do I create an object from another class (BlueJ)

I am making a program that simulates a Store and a Member. I am trying to write a method, memberRegister2(). This method is the the Store class but calls the constructor from the Member class to make a member object. This method is to be passed the name, id and pinNumber as parameters and then creates the Member object, which is to be stored in a local variable 'member'. I have no idea how to do this. As you will see from the code below I have tried to use the 'Member member = new Member()' But i do not know how to make the parameters user input.
(P.S I am using BlueJ)
Here is my code for both classes hopefully making my question make more sense. I am very new to java so excuse bad coding.
public class Store
{
// instance variables
private String storeName;
private int total;
//Member member;
/**
* Constructor for objects of class Store
*/
public Store(String newStoreName, int newTotal)
{
// initialise instance variables
storeName = newStoreName;
total = newTotal;
}
//Accessor Methods
public String getStoreName()
{
return storeName;
}
public int getTotal()
{
return total;
}
public void memberRegister1(Member newMember)
{
System.out.println("Salford Thrifty " + storeName + ": Welcome " + newMember.getName() + " (id:" + newMember.getId() + ")" );
}
public void memberRegister2()
{
//Member member = new member(memberName, memberId, memberPinNumber);
}
//Mutator Methods
public void newStoreName(String newName)
{
storeName = newName;
}
public void newTotal(int newTotal)
{
total = newTotal;
}
}
and the Member class
public class Member
{
// instance variables
private String name;
private String id;
private String pinNumber;
/**
* Constructor for objects of class Member
*/
public Member(String memberName, String memberId, String memberPinNumber)
{
// initialise instance variables
name = memberName;
id = memberId;
pinNumber = memberPinNumber;
}
public Member()
{
// initialise instance variables
name = "Bob";
id = "ASD123";
pinNumber = "5678";
}
//Accessor Methods
public String getName()
{
return name;
}
public String getId()
{
return id;
}
public String getPinNumber()
{
return pinNumber;
}
//Mutator Methods
public void newName(String newMemberName)
{
name = newMemberName;
}
public void newId(String newMemberId)
{
name = newMemberId;
}
public void newPinNumber(String newMemberPinNumber)
{
name = newMemberPinNumber;
}
}
I have been told to keep the variable at the top private and use pointers? Not sure what this means but it has not been explained to me very well.

You can a Scanner to read the user's input like so.
Scanner s = new Scanner(System.in);
String userInput = s.nextLine();
Then just initialize your member instance using the strings entered by the user.
String memberName, memberId, memberPin;
Scanner s = new Scanner(System.in);
System.out.println("Enter a name");
memberName = s.nextLine();
System.out.println("Enter an id");
memberId = s.nextLine();
System.out.println("Enter a pin");
memberPin = s.nextLine();
Member m = new Member(memberName, memberId, memberPin);
Also, you probably want to make pin, and maybe the id ints instead of strings.

Here's something I have from an old class that should show you how:
SavingsAccount myAccount = new SavingsAccount(200, 5);
So when you want to create an object from another class you have to use that second class to initialize it as shown above the SavingsAccount is like int it instantiates the object and then the two integers SavingsAccount(200, 5); is used because the method within the second class is instantiated with two integers of its own so the object you are creating must have two integers of its own. And what I mean by the method has two integer instantiated is as shown in the code below:
public SavingsAccount(double amount, double rate)
{
super(amount);
interestRate = rate;
}
if you do not instantiate a method with two objects within the parentheses then you do not need them within:
SavingsAccount myAccount = new SavingsAccount(200, 5);
I hope this helps any with your question i'm fairly new myself and am trying to help with as much as I can My course uses BlueJ as well and I know a good bit about BlueJ so I hope this helps.

Trouble creating an instance of a class in java

I am struggling with making this code work. Here is my code. First class:
public class PersonalAccount extends Account{
private String cardNumber;
private String cardType;
public ArrayList<PersonalAccount> personalAccounts;
public int personal;
private PersonalAccount(String first, String last, String accountNumber, String cardNumber, String cardType){
super(first, last, accountNumber);
this.cardNumber = "";
this.cardType = "";
}
public void addPersonalAccount(PersonalAccount aPersonalAccount){
personalAccounts.add(aPersonalAccount);
}
public void getNumberOfPersonalAccounts(){
personal = personalAccounts.size();
}
public void listAccounts(){
for (PersonalAccount personalaccount : personalAccounts){
System.out.println("Personal Accounts");
System.out.println(personalaccount);
}
}
public void findAccount(){
int index = 0;
boolean found = false;
while(index < personalAccounts.size() && !found){
PersonalAccount personalaccount = personalAccounts.get(index);
if (personalaccount.getaccountNumber().equals(accountNumber)){
found = true;
}else{
index++;
}
}
}
}
When attempting to create an instance of this class in another class, it instead creates an instance of the PersonalAccount object. Is there a way around this issue? I am very new to Java and BlueJ it should be noted.
EDIT: sorry I should clarify. I'm trying to call the methods from this class in another class. But when declaring
PersonalAccount class1 = new PersonalAccount();
I get the error: constructor PersonalAccount in class PersonalAccount cannot be applied to given types.
I am trying to call the method on a button click (where numAcc is the button):
numAcc.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent evt)
{
int personal;
personal = class1.getNumberOfPersonalAccounts();
}
});

You dont have a default constructor so you cannot create a PersonalAccount like this:
PersonalAccount class1 = new PersonalAccount();
You have to pass the parameters first, last, accountNumber, cardNumber, cardType. It should be something like this:
PersonalAccount class1 = new PersonalAccount("FirstName", "Last_Name", "123456", "123456789", "Visa");
Read this: http://www.dummies.com/how-to/content/how-to-use-a-constructor-in-java.html

You don't have a zero-argument constructor for PersonalAccount which is why the given statement would fail.
Is that the problem you are having?

The problem is here that the constructor is private:
private PersonalAccount(String first, String last, String accountNumber, String cardNumber, String cardType)
Two things:
You need to change your constructor such that it is public so that it is accessible:
public PersonalAccount(String first, String last, String accountNumber, String cardNumber, String cardType)
The next thing is to supply parameters such as first, last, accountNumber etc. However, if you declare: public PersonalAccount(), then you would not need to supply arguments when you instantiate the class.
You should now be able to call the methods of this class!