![]() ![]() Object get(Object key) : returns the value for the specified key in the HashMap.boolean containsValue(Object Value) : Similar to containsKey() method, it looks for the specified value instead of key.boolean containsKey(Object key) : returns true or false based on whether the specified key is found in the map or not.Object clone() : returns a shallow copy of the specified HashMap.void clear() : removes all the key-value pairs from the HashMap. ![]() List of methods in HashMap class and their short description. ("The key is :: " + entry.getKey() + ", and value is :: " + entry.getValue() ) Iterator> entryIterator = map.entrySet().iterator() ("The key is :: " + key + ", and value is :: " + value ) Please note that iterators of this class are fail-fast and if any structure modification is done after creation of iterator, it will throw ConcurrentModificationException. Remove pair by key – HashMap.remove() HashMap map = new HashMap() Get value by key – HashMap.get() HashMap map = new HashMap() Add key-value using Map.put() HashMap map = new HashMap() Let’s quickly go through some examples to work with HashMap in Java. Then all elements are iterated in the LinkedList, and the correct value object is found by identifying the correct key using its equals() method. While retrieving the value by key, the first index location is found using key’s hashcode. In case of collision, where multiple keys are mapped to a single index location, a linked list is formed to store all such key-value pairs that should go in a single array index location. This hash value is used to calculate the index in the array for storing Entry object. For each key-value to be stored in HashMap, a hash value is calculated using the key’s hash code. static class Entry implements Map.EntryĪll instances of Entry class are stored in an array declared as 'transient Entry table'. The key-value pairs are stored as instances of the inner class HashMap.Entry which has key and value mapping stored as attributes. Each object in java has it’s hash code in such a way that two equal objects must produce the same hash code consistently. Hashing is a way to assigning a unique code for any variable/object after applying any formula/algorithm on its properties. HashMap implements Cloneable and Serializable interfaces.So primitives must be used with their corresponding wrapper classes. HashMap stores only object references.A value can be retrieved only using the associated key. ![]() Or you can use Collections.synchronizedMap(hashMap) to get the synchronized version of HashMap. You must explicitly synchronize concurrent modifications to the HashMap. It does not guarantee any specific order of the elements.
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