package com.test;
import java.util.Collection;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;
public class MutliMapTest {
public static void main(String... args) {
Multimap<String, String> myMultimap = ArrayListMultimap.create();
// Adding some key/value
myMultimap.put("Fruits", "Bannana");
myMultimap.put("Fruits", "Apple");
myMultimap.put("Fruits", "Pear");
myMultimap.put("Fruits", "Pear");
myMultimap.put("Vegetables", "Carrot");
// Getting the size
int size = myMultimap.size();
System.out.println(size); // 5
// Getting values
Collection<String> fruits = myMultimap.get("Fruits");
System.out.println(fruits); // [Bannana, Apple, Pear, Pear]
System.out.println(ImmutableSet.copyOf(fruits));// [Bannana, Apple, Pear]
// Set<Foo> set = Sets.newHashSet(list);
// Set<Foo> foo = new HashSet<Foo>(myList);
Collection<String> vegetables = myMultimap.get("Vegetables");
System.out.println(vegetables); // [Carrot]
// Iterating over entire Mutlimap
for (String value : myMultimap.values()) {
System.out.println(value);
}
// Removing a single value
myMultimap.remove("Fruits", "Pear");
System.out.println(myMultimap.get("Fruits")); // [Bannana, Apple, Pear]
// Remove all values for a key
myMultimap.removeAll("Fruits");
System.out.println(myMultimap.get("Fruits")); // [] (Empty Collection!)
}
}
这里有一点你可能会疑惑，就是为何get方法返回的是一个collection而不是list，这是因为前者会更加有用。如果你需要基于multimap直接操作list或者set，那么可以使用在定义类型的时候使用子类名称：ListMultimap，SetMultimap和SortedSetMultimap。例如：
ListMutlimap<String,String> myMutlimap = ArrayListMultimap.create();
List<string> myValues = myMutlimap.get("myKey"); // Returns a List, not a Collection.
另外，静态工具类
Multimaps的asMap可以返回具体类型的map。
static <K,V> Map<K,List<V>> asMap(ListMultimap<K,V> multimap)
Returns multimap.asMap(), with its type corrected from Map<K, Collection<V>> to Map<K, List<V>>.
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