gives key/value from 30 to last and includes 30 SortedMap hm = map1.headMap( new Integer(50)) gives key/value from first to 50 and excludes 50 println(ntainsValue( new Double(33.33))) cannot add different type of keys in TreeMap can add different type of value in TreeMap using same key will update or replace the value Null keys are not allowed but null values. TreeMap uses tree data structure to store the keys.ĭuplicate keys are not allowed but duplicate values are allowed. TreeMap is implementing SortedMap interface. There are many different implementations of the Map interface. However we can obtain a collection-view of a map, which does allow the use of either the for loop or an iterator. This means that we cannot cycle through a map using a for-each style for loop and we can’t obtain an iterator to a map. They don’t implement the Iterable interface. To do this, we can use the entrySet( ) method, to obtain a collection-view of the keys, use keySet( ). However, you can obtain a collection-view of a map. The value is returned.Īlthough part of the Collections Framework, maps are not, themselves, collections because they do not implement the Collection interface. To obtain a value, call get( ), passing the key as an argument. To put a value into a map, use put( ), specifying the key and the value. Maps revolve around two basic operations: get( ) and put( ). After the value is stored, we can retrieve it by using its key. Given a key and a value, we can store the value in a Map object. A key is an object that we use to retrieve a value at a later date. The Map interface maps unique keys to values. Some maps can accept a null key and null values, others cannot. The keys must be unique, but the values may be duplicated. StringbufferĪ map is an object that stores associations between keys and values, or key/value pairs.
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