How-to articles, tricks, and solutions about HASHMAP

In Java, the HashMap class is the equivalent of the Dictionary class in C#. It is a map data structure that stores (key, value) pairs and provides fast lookup and insertion of elements.

To get the string value from a HashMap depending on the key name in Java, you can use the get() method of the Map interface.

To get the first key-value pair from a HashMap in Java, you can use the entrySet() method to get a set of the map's entries and then use the iterator() method to get an iterator for the set.

To sort the values of a Map by key in Java, you can use the TreeMap class, which is a Map implementation that maintains its entries in ascending key order.

To convert a List to a Map in Java, you can use the stream() method and the collect() method along with a Collectors.toMap() call. Here's an example of how to do this:

To get the values and keys from a HashMap in Java, you can use the values and keySet methods.

To sort a HashMap in Java, you can use the TreeMap class, which is a Map implementation that maintains its entries in ascending order, sorted according to the keys.

To update the value associated with a key in a HashMap in Java, you can use the put() method.

In PHP, the equivalent to a Java HashMap would be an associative array.

There are several ways to iterate through a HashMap in Java: Using the for-each loop

To compare two lists in Java, you can use the equals() method of the List interface.

To get the key for a given value in a java.util.HashMap, you can use the entrySet() method of the java.util.HashMap class to get a set of the mappings in the map, and then iterate over the set and check the value of each mapping.

To check if a key exists in a HashMap in Java, you can use the containsKey method.

To sort a HashMap by values in Java, you can use the Map.Entry interface and the Comparator interface to create a comparator that compares the values in the map.

There are several differences between a HashMap and a Hashtable in Java:Synchronization: Hashtable is synchronized, while HashMap is not.