JavaScript objects in Java?

Question

How do I loop over a string of item and create an object based on that?

I currently have this code:

public static Object ParseParams(String string)
{
    Object params = new Object();
    String[] lines = string.split("\n");
    for(String line : lines)
    {
        String[] splittedLine = line.split("=");
        params[splittedLine[0]] = splittedLine[1]; //JavaScript syntax, not Java!
    }
    return params;
}

The input string is in this format:

param1=value1
param2=value2
foo=bar

How do I fix the problematic line?

Edit

Sometimes the string would look like this:

foo=bar
param=1=hello
param=2=world

Would it be possible with Maps in Java to get the output like this:

foo
  bar
param
  1
    hello
  2
    world

So the Maps are sometimes nested, and it you would retrieve hello by calling params.get("param").get("1");

Oh, that's not how objects in Java work at all. You may want to stick with a Map implementation like HashMap, or use a JSON library if that's your end goal. — Dave Newton
– Dave Newton, Commented Oct 31, 2011 at 23:47

Community · Accepted Answer · 2017-05-23 12:11:31Z

3

It sounds like you want either a Map, or a JSON library.

Maps

public static Map<String, String> ParseParams(String string)
{
    Map<String, String> params = new HashMap<String, String>();
    String[] lines = string.split("\n");
    for(String line : lines)
    {
        String[] splittedLine = line.split("=");
        params.put(splittedLine[0], splittedLine[1]);
    }
    return params; // Get a param with params.get(key);
}

In general you'll want a HashMap (fast but not stored in order), but there's also a TreeMap which is slightly slower but stored in order (which can be useful sometimes).

JSON

The format JavaScript uses for objects is used as a general-purpose storage format called JSON (JavaScript Object Notation). This is only useful for storage / printing / network transmission. Internally, Java JSON libraries use maps (JavaScript interpreters probably do too).

There are several Java APIs, but StackOverflow users seem to recommend Json-lib:

public static JSONObject ParseParams(String string)
{
    // Note that we need everything from the other method anyway
    return JSONObject.fromObject(ParseParams(string));
}

EDIT:

You're already reaching the point where using a Map is strained. I'd suggest just using a class:

class MyStuff {
    String foo;
    Map<String, String> params;
}

It is possible to nest Maps, like Map<String, Map<String, String>> or Map<String, Object>, but you really should be using classes for this.

edited May 23, 2017 at 12:11

CommunityBot

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answered Oct 31, 2011 at 23:49

Brendan Long

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3 Comments

Tyilo Over a year ago

Thank you very much, could you please take a look at my edit of the question?

Tyilo Over a year ago

<noobQuestion>How would you do that with classes?</noobQuestion>

Brendan Long Over a year ago

@Tylio - Sorry, I don't think I could give a decent introduction to classes. You could try the Java Tutorial.

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