java - Properties file with a list as the value for an individual key

Question

For my program I want to read a key from a properties file and an associated List of values for the key.
Recently I was trying like that

public static Map<String,List<String>>categoryMap = new Hashtable<String, List<String>>();


    Properties prop = new Properties();


    try {

        prop2.load(new FileInputStream(/displayCategerization.properties));
        Set<Object> keys = prop.keySet();
        List<String> categoryList = new ArrayList<String>();
        for (Object key : keys) {
            categoryList.add((String)prop2.get(key));
            LogDisplayService.categoryMap.put((String)key,categoryList);
        }
        System.out.println(categoryList);
        System.out.println("Category Map :"+LogDisplayService.categoryMap);

        keys = null;
        prop = null;

    } catch (Throwable e) {
        e.printStackTrace();
    }

and my properties file is like below -

A=APPLE
A=ALPHABET
A=ANT
B=BAT
B=BALL
B=BUS

I want for key A there should be a list which contain [APPLE, ALPHABET,ANT] and B contain [BAT,BALL,BUS].
So Map should be like this {A=[APPLE, ALPHABET,ANT], B=[BAT,BALL,BUS]} but I get
{A=[ANT], B=[BUS]}
I searched on the internet for such a way but found nothing. I wish there should be a way. Any help?

Answer 1

Try writing the properties as a comma separated list, then split the value after the properties file is loaded. For example

a=one,two,three
b=nine,ten,fourteen

You can also use org.apache.commons.configuration and change the value delimiter using the AbstractConfiguration.setListDelimiter(char) method if you're using comma in your values.