Key-value collection with convenient notation

Question

I am looking for a Map-like collection that would allow me to create new object in a PHP/Python/JavaScript way:

var foo = new Foo({'foo': 'bar'})

The closest I have in Java is HashMap:

Map<String, String> parameters = new HashMap<String, String>();
parameters.put("test", "one two");
parameters.put("foo", "bar");

This is too verbose for my purpose. I would like to write down and handle over key-value pairs in an easier way.

I welcome any suggestions - creating own type of collection, creating own factory for a Map object etc. I just want to axe number of characters needed to write down to create such a collection.

see http://stackoverflow.com/questions/6833925/better-map-constructor/6833946#6833946 — Nathan Hughes, Aug 14 '11 at 15:12

score 3 · Answer 1 · answered Aug 14 '11 at 15:13

3

You have the (not very well-known) double brace initialization trick:

Map<String, String> Map = new HashMap<String, String>() {{
      put("test", "one two");
      put("foo", "bar");
}};

With java 7 diamond operator this is even more succinct, see:

Map<String, String> Map = new HashMap<>() {{
      put("test", "one two");
      put("foo", "bar");
}};

answered Aug 14 '11 at 15:13

Pablo Fernandez

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http://stackoverflow.com/questions/924285/efficiency-of-java-double-brace-initialization – NimChimpsky Aug 14 '11 at 15:22

score 3 · Accepted Answer · answered Aug 14 '11 at 15:17

A way I've seen, when sticking to the base JDK, is to just use anonymous initializers:

Map<String, String> parameters = new HashMap<String, String>() {{
  put("test", "one two");
  put("foo", "bar");
}};

You can also take a look at the Guava ImmutableMap builder: http://guava-libraries.googlecode.com/svn/trunk/javadoc/com/google/common/collect/ImmutableMap.Builder.html

If you want to get a little far out there you could write a parser for something like JSON (or just JSON itself and a JSON library) and then write the Map as a string.

Thank you! I'll go with the double brace trick, but the JSON suggestion is also nice. — Ondřej Mirtes, Aug 14 '11 at 15:29

Key-value collection with convenient notation

2 Answers2