When to use Properties and when Map in Java?

Question

Difference between Map and Properties as both have key-value pair.

Answer 1

A Properties object is a Map. See for example http://java.sun.com/javase/6/docs/api/java/util/Properties.html. I.e. the Properties class implements the Map interface.

Answer 2

Properties is mainly used for based configuration data and localization, while Map is more general-purpose.

Answer 3

According to the docs,

• Map is an interface
• Properties is a class that implements that interface

Answer 4

Properties IS-A Map which IS-A Hashtable. Whether it should or not is a different question - I think it should really get the Map through composition and not implementing the Map interface.

Properties class is for Properties files - that's why it has load methods on it to read the file in. So if you're working with properties files e.g.

propa = bob
propb = jane

then use Properties. Otherwise you'll want to create your own Map interface and pick an appropiate implementation e.g. HashMap

Answer 5

The Properties Class implements the Map-Interface. The Properties Class has Methods to save its content to a Stream.

look at: http://java.sun.com/j2se/1.3/docs/api/java/util/Properties.html

If you do not need to save the content, stay with a "normal" Map Implementation like HashMap

Answer 6

A map is meant for normal key-value pair usage in code. Properties are typically used for storing and loading configuration values from a file. The underlying implementation of a Properties uses a Map.

See the link below for a quick tutorial on how and when to use Properties.

http://docs.oracle.com/javase/tutorial/essential/environment/properties.html