How to return HashMap object fields

Question

I currently have the following HashMap in a Holiday class.

Holiday Class:

HashMap <String, Location> holidays = new HashMap<String, Location>();

This creates an instance of the Location class, to allow more fields to be shown.

Location class:

public class Location {
private String locationName;
private String locationDesc;
private double price;
private int quantity;

public Location(String locationName, String locationDesc, double price) {
    this.locationName = locationName;
    this.locationDesc = locationDesc;
    this.price = price; 
    quantity = 0;
}

public String toString() {
    return (locationName + " | " + "£" + price);
}
public double getPrice() { return price; }
public String getLocationName() { return locationName; }
public String getLocationDesc() { return locationDesc; }
public int getQuantity() { return quantity; }
}

In my GUI class I just use the .get HashMap method, this will return the toString. e.g

GUI class

private Holiday holiday;
...
return holiday.holidays.get(--HashMap key here--);

this will return the toString, which is locationName and price.

However. I'm wanting to also print out the HashMap elsewhere, but with returning different fields. such as returning the Description and quantity as well as locationName and price. How would i go about doing this? Or how do i return the individual fields from the Location class which is an instance of in the HashMap.

MANAGED TO DO THIS. But need help with the following below

Second EDIT:

I have a set quantity method in my Location class, to set the amount of bookings for each holiday. However when using;

for (Location location : holiday.holidays.values()) {
location.setQuantity(Integer.parseInt(textFieldQuantity.getText()));
}

This changes all of the holidays to the same quantity when setting each location with a different quantity. How do i fix this?

`Holiday.holidays.get` returns a `Location` object, not a string. And you can get anything inside it using the `getPrice()`, `getlocationName()` and other getter methods. — RealSkeptic, Mar 13 '15 at 16:56
Why don't you iterate over the `HashMap` entries and build a `String` with all the fields you want from each `Location` object? — fps, Mar 13 '15 at 16:57
Read the stack trace of the exception. And read this: http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it — JB Nizet, Mar 13 '15 at 17:20
Just altered the code so it tries to add it into the list instead of printing it. I get the NullPointerException on the .addElement line. How do i fix it? — james11, Mar 13 '15 at 17:29

Anderson Vieira · Accepted Answer · 2015-03-14T18:04:28.400

The result of holidays.get(key) should be an object of type Location. If you print the object directly, like in System.out.println(holidays.get(key)) it will print the result of toString() as you say. But since you already have the object and access to its fields, you can print exactly what you want.

Something like this should work:

Location location = holidays.get(key);
System.out.println(location.getlocationDesc() + " | " + location.getQuantity());

Regarding your second question:

If you just need to print all values stored in your map, I think it would be cleaner and faster to iterate directly on the map values:

for (Location location : holiday.holidays.values()) {
    System.out.println(location.getlocationDesc() + " | " + location.getQuantity());
}

Third question:

Note that your code does not set the quantity for only one location. It goes through all locations setting each quantity to the same value, defined by textFieldQuantity.getText().

If you want to modify a specific location, you need to retrieve it from the map using get():

Location location = holiday.holidays.get(key);
location.setQuantity(Integer.parseInt(textFieldQuantity.getText()));

This works - i've added an edit at the bottom of the post, by trying to iterate through it and add them to the JList. How do i fix that issue? — james11, Mar 13 '15 at 17:13
Having an issue with using the setQuantity method within Location. When i set a quantity for one holiday within the list, it changes this for all of them. How do i fix this? Seems to be an issue with this for loop for doing it- – Added this as second edit on original question. — james11, Mar 14 '15 at 16:24

score 0 · Answer 2 · answered Mar 13 '15 at 16:57

0

Why not try something like:

private Location location = holiday.holidays.get(--HashMap key here--);

// Create a string with the variables

And then return the string.

answered Mar 13 '15 at 16:57

xscanpix

76
1
4

score 0 · Answer 3 · answered Mar 13 '15 at 16:57

this will return the toString, which is locationName and price

No. It will return an instance of Location. So all you have to do is

Location location = holiday.holidays.get("some key");
double price = location.getPrice();
String locationName = location.getLocationName();

Note that

you shouldn't use public fields. So it should be instead location.getHolidays().get("some key"). Or even better, to encapsulate the Map and respect the "don't talk to strangers" rule, location.getHoliday("some key").
Your getter should be named getLocationName() and not getlocationName() to respect the JavaBean conventions. Or even better, since this method is part of a Location class, the location prefix is redundant, and you should thus simply name it getName() (and getDescription() for the description)

How to return HashMap object fields

3 Answers3