Question

Hi I have a strange question about java. I will leave out the background info so as not to complicate it. If you have a variable named fname. And say you have a function returning a String that is “fname”. Is there a way to say reference the identifier fname via the String “fname”. The idea would be something like “fname”.toIdentifier() = value but obviously toIdentifier isn’t a real method.

I suppose a bit of background mite help. Basically I have a string “fname” mapped to another string “the value of fname”. And I want a way to quickly say the variable fname = the value of the key “fname” from the map. I’m getting the key value pair from iterating over a map of cookies in the form . And I don’t want to do “if key = “fname” set fname to “value of fname” because I have a ton of variables that need to be set that way. I’d rather do something like currentkey.toIdentifer = thevalue. Weird question maybe I’m overlooking a much easier way to approach this.

Answer 1

In a way you’re describing what reflection is used for:

You refer to an object’s fields and methods by name.

• Java Reflection

However, most of the time when people ask a question like this, they’re better off solving their problem by re-working their design and taking advantage of data structures like Maps.

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Here’s some code that shows how to create a Map from two arrays:

String[] keyArray = { "one", "two", "three" };
String[] valArray = { "foo", "bar", "bazzz" };

// create a new HashMap that maps Strings to Strings

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

// create a map from the two arrays above

for (int i = 0; i < keyArray.length; i++) {
    String theKey = keyArray[i];
    String theVal = valArray[i];
    exampleMap.put(theKey, theVal);
}

// print the contents of our new map

for (String loopKey : exampleMap.keySet()) {
    String loopVal = exampleMap.get(loopKey);
    System.out.println(loopKey + ": " + loopVal);
}

Here’s a link to the JavaDoc for Map.