Java - Properties: Add new keys to properties file in run time?

java properties runtime key add
Olcay Ertaş picture Olcay Ertaş · Sep 27, 2011 · Viewed 21.6k times · Source

Is it possible to create a new properties file and add keys and values in run time? I want to add new keys to properties file depending on user input while installing my application. I checked out Java Properties class but it seem it can set values to existing keys but can not add new keys to properties file.

Answer

Jon Skeet picture Jon Skeet · Sep 27, 2011

You can add new properties just by calling setProperty with a key which doesn't currently exist. That will only do it in memory though - you'll have to call store again to reflect the changes back to a file:

Properties prop = new Properties();
prop.load(...); // FileInputStream or whatever

prop.setProperty("newKey", "newValue");
prop.store(...); // FileOutputStream or whatever

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