C# to Java - Dictionaries?
Solution 1:
This will do what you want:
Map<String,Integer> map = new HashMap<String, Integer>(){{
put("cat", 2);
put("dog", 1);
put("llama", 0);
put("iguana", -1);
}};
This statement creates an anonymous subclass of HashMap, where the only difference from the parent class is that the 4 entries are added during instance creation. It's a fairly common idiom in the Java world (although some find it controversial because it creates a new class definition).
Because of this controversy, as of Java 9 there is a new idiom for conveniently constructing maps: the family of static Map.of methods.
With Java 9 or higher you can create the map you need as follows:
Map<String, Integer> map = Map.of(
"cat", 2,
"dog", 1,
"llama", 0,
"iguana", -1
);
With larger maps, this alternative syntax may be less error-prone:
Map<String, Integer> map = Map.ofEntries(
Map.entry("cat", 2),
Map.entry("dog", 1),
Map.entry("llama", 0),
Map.entry("iguana", -1)
);
(This is especially nice if Map.entry is statically imported instead of being referenced explicitly).
Besides only working with Java 9+, these new approaches are not quite equivalent to the previous one:
- They don't allow you to specify what Map implementation is used
- They only create immutable maps
- They don't create an anonymous subclass of Map
However, these differences shouldn't matter for many use cases, making this a good default approach for newer versions of Java.
Solution 2:
Map<String,Integer> map = new HashMap<String, Integer>(){{
put("cat", 2);
put("dog", 1);
put("llama", 0);
put("iguana", -1);
}};
Solution 3:
Bite the bullet and type out the map name!
Map<String, Integer> map = new HashMap<String, Integer>();
map.put("cat", 2);
map.put("dog", 1);
map.put("llama", 0);
map.put("iguana", -1);
You could also do something like this, which might save some typing with a long list:
Object[][] values = {
{"cat", 2},
{"dog", 1},
{"llama", 0},
{"iguana", -1}
};
for (Object[] o : values) {
map.put((String) o[0], (Integer) o[1]);
}