Java .properties read Strings with the same name

[cerulean knoll]

Ok so I got a .properties file in my Project and now, I would like to read every single property, which starts with "API" in this example and return it as a list or something, how can I do that

[old imp]

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[wicked barn]

You can either iterate over all keys in properties and filter all that start with "API", or use streams

Depends how you are currently reading your properties

[cerulean knoll]

like this

and resources

[wicked barn]

So you have a Properties object, right?

[cerulean knoll]

yes

[wicked barn]

Okay, sec

[wicked barn]

So basically, you want to read all properties that start with specified string and store it in a list right? So in this example you expect to get a list containing just the api links?

[cerulean knoll]

yes

indeed

[wicked barn]

So you have two options. Let me start with the one that is fairly simple to understand.

Properties props = ...

List<String> api_links = new ArrayList<>();

for(Map.Entry<Object, Object> entry : props.entrySet()) {
    if(entry.getKey() instanceof String key && key.startsWith("API")) {
        Object value = entry.getValue();
        if(value instanceof String valueString) {
            api_links.add(valueString);
        }
    }
}

So, you can iterate over all entries in your Properties object

Properties extends a map, so it also has an entrySet method, which returns a set of entries in this properties object

You can then check every key one by one if it starts with desired string ("API" in your case), and if it does, just add a value associated with current entry to a List created before

[cerulean knoll]

ok I see

[wicked barn]

You should do instanceof checks, because Properties#entrySet() returns a set of <Object, Object> pairs, so it's safer to check if these Objects are Strings for sure

[cerulean knoll]

Ok I see, now what do I call or use to uhm write for example the first API thing into a string or something

like where will the links be saved

[wicked barn]

In this example it will be the api_links List, it should contain all links read from Properties

[cerulean knoll]

api_links[]

ojk ye

I can just iterate through that list using .length right

[wicked barn]

size(), but yeah

[cerulean knoll]

ok

do I need .getProperty also or no

No

Cuz its already saved in the list right

[wicked barn]

Yeah

[cerulean knoll]

ok

[wicked barn]

This list is completely independent from the Properties object

[cerulean knoll]

ok good

ok thats it I guess

thanks men

[old imp]

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[wicked barn]

You are welcome

[cerulean knoll]

uh another question rq

How do I create such a list, with as much elements as a method for example needs

cuz I got a vars.java file where all read properties are saved as static

would this work

[wicked barn]

Depends on what you want to achieve, but if your file looks roughly like this:

public static class Vars {
  public static List<String> apis;

  public static void setApis(List<String> api) {
    apis = api
  }
}

then that should work. You will be able to access the same list by just calling Vars.apis

[cerulean knoll]

ok, will Vars.apis return single strings or

god ive never used this, that shit is breaking my brain

[wicked barn]

It returns the very same List you passed with setApis

setApis just assigns your list to a variable in the class

[cerulean knoll]

ok it wokred

fire

ok for now ill try to work w that

thanks mate

[old imp]

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If you are not, please ignore this message.
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