Question

Guava offers a nice shortcut for initializing a map. However I get the following compiler error (Eclipse Indigo) when my map initializes to nine entries.

The method of(K, V, K, V, K, V, K, V, K, V) in the type ImmutableMap is not applicable for the arguments
(String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String, String)

ImmutableMap<String,String> myMap = ImmutableMap.of(
        "key1", "value1", 
        "key2", "value2", 
        "key3", "value3", 
        "key4", "value4", 
        "key5", "value5", 
        "key6", "value6", 
        "key7", "value7", 
        "key8", "value8", 
        "key9", "value9"
        );

The message appears to say that

An ImmutableMap has a maximum size of four pairs of key,value.

Obviously, this cannot be the case but I can’t figure out what to do to increase the size of my initializer.

Can someone tell me what is missing?

Answer 1

Notice that your error message only contains five K, V pairs, 10 arguments total. This is by design; the ImmutableMap class provides six different of() methods, accepting between zero and five key-value pairings. There is not an of(...) overload accepting a varags parameter because K and V can be different types.

You want an ImmutableMap.Builder:

ImmutableMap<String,String> myMap = ImmutableMap.<String, String>builder()
    .put("key1", "value1") 
    .put("key2", "value2") 
    .put("key3", "value3") 
    .put("key4", "value4") 
    .put("key5", "value5") 
    .put("key6", "value6") 
    .put("key7", "value7") 
    .put("key8", "value8") 
    .put("key9", "value9")
    .build();