Getting a HashMap and using it in another class

Hey.

DeathBan class:

Code:

public HashMap<String, Long> deathbanned;

    public DeathBan() {
        this.deathbanned = new HashMap<String, Long>();
    }

// code
// code

Border class:

Code:

 // player event
       DeathBan db = new DeathBan();
             db.deathbanned.put(playerName, System.currentTimeMillis());

This doesn't work. The player's name (string) doesn't get added to the HashMap in the Border class.

 

@Vamure
Of course it doesn't work. You just created a new DeathBan instance and added the name to it inside which in turn does really nothing.

 

@Gater12 lol

 

Just make the HashMap static

 

@BugsyFTW If I wasn't too lazy to find a facepalm picture, there'd be a huge one right here.

*Facepalm*

 

http://bukkit.org/threads/how-to-us...-that-extends-javaplugin.285074/#post-2613361

http://bukkit.org/threads/using-a-string-in-different-classes.184140/#post-1916182

 

Great example of my signature.

http://docs.oracle.com/javase/tutorial/java/javaOO/arguments.html

 

Whats wrong with making static HashMaps?

 

Static isn't a tool to make accessing fields easier. What if you had this:

Code:java

public class MyClass {
    public static Map<?, ?> myMap = new HashMap<>();
}

How would you handle me doing this?:

Code:java

MyClass.myMap = null;

You could of course add a final modifier to the map, but it's the same principle:

Code:java

MyClass.myMap.clear();

If you blatantly expose your fields in a class then you open yourself to hours of frustration later in trying to track down things that call your map badly, having to implement solutions like:

Code:java

public static final Map<String, String> myMap = new HashMap<String, String>() {
 
    @Override
    public void clear() {}
 
    @Override
    public String remove(String remove) {
        StackTraceElements[] elm = Thread.getCurrentThread().getStackTrace();
        if (elem.length > 2) {
            //conditional code on calling depending on class members
        }
    }
 
}

Whereas you can simply just use mutator and getter statements to allow only the functionality you desire:

Code:java

private final Map<String, String> myMap = new HashMap<>();
 
public Map<String, String> getMap() {
    return Collections.unmodifiableMap(this.myMap);
}
 
public String getValue(String key) {
    return this.myMap.get(key);
}

The whole point of this is that you should try to make a class as unmodifiable as possible while still allowing the operations you want.

 

http://bukkit.org/threads/static-object-of-main-class.338854/#post-3001984

 

Uh, I did try this:

private DeathBan db;

// constructor
this.db = new DeathBan();

// event
this.db.deathbanned.put(playerName, System.currentTimeMillis());

 

Instead of creating a new DeathBan instance, you should pass your other one via constructor.