Tutorial Save and load HashMap to/from config

Because so many people didn't know how to save & load HashMaps, I made this tutorial.

This is your example HashMap:

Code:Java

HashMap<Object, Object> hm = new HashMap<Object, Object>();

("Hey, my HashMap is not <Object, Object>!" --> Read the last bit of this tutorial)

This will be our method to save the HashMap:

Code:Java

public void saveHashMap(HashMap<Object, Object> hm) {
}

Inside it, we loop through every key in the HashMap and set the key + value to the config:

Code:Java

for (Object key : hm.keySet()) {
config.set("HashMap."+key, hm.get(key));
}
//important: save the config!
saveConfig();

Our next method is to load the HashMap:

Code:Java

public HashMap<Object, Object> loadHashMap() {
HashMap<Object, Object> hm = new HashMap<Object, Object>();
 
 
return hm;
}

Before we return the HashMap, this bit is needed to load the keys + values.
Loop through the ConfigurationSection where you saved the HashMap (in this case it's "HashMap").
Next put the key + value in the Hashmap.

Code:Java

for (String key : config.getConfigurationSection("HashMap").getKeys(false)) {
hm.put(key, config.get("HashMap."+key));
}

Done


Last bit:
HashMap is not <Object, Object>
If your HashMap is for example <String, Integer>
then just replace all <Object, Object> with <String, Integer>.
And you need to cast/load the keys + values in the loadHashMap method differently. Something like this:

Code:Java

hm.put(key, config.getInt("HashMap."+key));

All methods used (open) All methods used (close)

Code:java

public void saveHashMap(HashMap<Object, Object> hm) {
for (Object key : hm.keySet()) {
config.set("HashMap."+key, hm.get(key);
}
saveConfig();
}
 
public HashMap<Object, Object> loadHashMap() {
HashMap<Object, Object> hm = new HashMap<Object, Object>();
for (String key : config.getConfigurationSection("HashMap").getKeys(false)) {
hm.put(key, config.get("HashMap."+key));
}
return hm;
}

 

@FisheyLP Isn't this kind of pointless since I am assuming SnakeYAML does this for you?

 

Nice, Its very helpfuly for new developers

 

@FisheyLP Well ... this is about storing data in a HashMap okay =) Then i need to correct something.

When you define the object please use its Interface.

In your case use

Code:java

 
Map<String, String> hm = new HashMap<String, String>();
 

instead of HashMap<String, String> hm = ...

Also always use them when you define getter or setter.

As already pointed out the Configuration Class has many setter and getter for almost any Object like getAsInt, getAsString etc ...

 

1. How to load the Map from a FileConfiguration:

Code:

// If you want to set to the root, remove getConfigurationSection()
Map<String, ?> map = config.getConfigurationSection("path").getValues(true or false);

2. How to save the Map to a FileConfiguration:

Code:

config.createSection("path.or.leave.empty.for.root", map); // Will in fact override any existing values

 

Cleared Offtopic conversation.
This is a Bukkit Resource, not a place where you can discuss the complexity and value of a totally different Thread which was locked for a valid reason.

 

Code:

for (Object key : hm.keySet()) {
    config.set("HashMap."+key, hm.get(key));
}

Efficiency -1

 

Why not tell him the right way to do it rather than just saying that?

The reason why it is less efficient is because you're iterating over the map and then iterating over it again to find the values, you should just use an EntrySet.

Code:

Map<String, Object> someMap = new HashMap<String, Object>();
for(Map.Entry<String, Object> entry : someMap.entrySet()) {
    config.set("HashMap."+entry.getKey(), entry.getValue());
}

 

No use if he doesn't care.

 

Then there is no use commenting on his thread. Or you can just continue being hypocritical. But the latter isn't a very respectable or valuable in any way, so you probably should just buzz off.

 

When using a <UUID, String> HashMap, getConfigurationSection gives this error: Type mismatch: cannot convert from element type String to UUID.

Code:java

 
    public HashMap<UUID, String> loadHashMap(){
        HashMap<UUID, String> rank = new HashMap<UUID, String>();
        for(UUID key : getConfig().getConfigurationSection("HashMap.").getKeys(false){
            rank.put(key, getConfig().getString("HashMap."+key));
        }
        return rank;
    }
 

When changing it to a String, you can't put it in the rank HashMap, because The method put(UUID, String) in the type HashMap<UUID,String> is not applicable for the arguments (String, String).

How can I fix this?