Converting java.util.Properties to HashMap<String,String>

Question

Properties properties = new Properties();
Map<String, String> map = new HashMap<String, String>(properties);// why wrong?

java.util.Properties is a implementation of java.util.Map, And java.util.HashMap's constructor receives a Map type param. So, why must it be converted explicitly?

Answer 1

This is because Properties extends Hashtable<Object, Object> (which, in turn, implements Map<Object, Object>). You attempt to feed that into a Map<String, String>. It is therefore incompatible.

You need to feed string properties one by one into your map...

For instance:

for (final String name: properties.stringPropertyNames())
    map.put(name, properties.getProperty(name));