Difference Between HashMap vs. Hashtable in Java

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Main Difference

The difference between HashMap and Hashtable in java is that HashMap implements the Map interface and is unsynchronized whereas Hashtable extends the Dictionary class and is synchronized.

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HashMap vs. Hashtable in Java

Java is an object-oriented programming language that uses both compiler and interpreter. Mostly all software’s are made in Java programming language. Java code can be written on Windows, Linux, and Mac OS. The syntax of C and C++ programming language is quite the same. Java produces browser to run programs that help in making a graphical user interface. Java programming language is in used and trend these days. To write Java code, a programmer needs software development kit (SDK) that includes a compiler, interpreter that is not required in C++. Group of objects are represented by HashMap and HashTable, the way to represent a group of objects is <Key, Value>. HashMap and HashTable are the examples of the list in java. The list is an interface that extends the collection interface. The list is a collection of ordered element and elements are added, removed and accessed with the help of an index variable. There cannot be any duplicate elements in sets, but there can be duplicate elements in the list. There are some common methods in list that are index-based get() and set() method. There are also add a () method that is used to add elements in the list, and another method removes () that is used to remove elements in the list. We can also say that list is a kind of array that can grow size as we add elements in the list. There is no method to set the range of indexed in a list. There is just a sub list() method that returns sub list from the original list of a specific range. If we talk about the main difference between hashMaps and hashTables, then the main difference between HashMap and Hashtable in java is that HashMap implements the Map interface and is unsynchronized whereas Hashtable extends the Dictionary class and is synchronized. A map based collection that is used for key and value pair is known as HashMap. There is a pair that is <Key, Value>. Order of the key and value is fixed. HashMap is very similar to Hashtable. Key and values are not returned in the same way as it is stored or inserted in Hashtable. The most important thing is to import the file java.util.HashMap. Void clear() removes all the keys form the HashMap. Object clone() returns a copy of all the mapping. Boolean contains key() returns true or false based on key. Value get() returns the value of specific key. Set key Set() returns the key fetched from the map. Hashtable extends the Dictionary class and is synchronized. In binary search data structures can improve the efficiency of searches. The efficiency of search is increasing from O(n) to O(logn) by using binary search. Hash table is an example of a data structure. There are two parts of the hash table that is an array that is an actual table where data to be searched is stored and is called mapping function. The second type is a hash function that is a mapping from the input space to the integer space that defines the indices of the array.

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Comparison Chart

BasisHashMapHashtable
MeaningHashMap implements the Map interface and is unsynchronizedHashtable extends the Dictionary class and is synchronized.
SynchronizedHashMap is unsynchronizedHashtable is synchronized
Null valueHashMap cannot return a Null valueHashtable can return a Null value
TraverseHashMap cannot be traverse directlyHashtable can be traverse directly

What is HashMap?

A map based collection that is used for key and value pair is known as HashMap. There is a pair that is <Key, Value>. Order of the key and value is fixed. HashMap is very similar to Hashtable. Key and values are not returned in the same way as it is stored or inserted in Hashtable. The most important thing is to import the file java.util.HashMap. Void clear() removes all the keys form the HashMap. Object clone() returns a copy of all the mapping. Boolean contains key() returns true or false based on the key. Value get() returns the value of the specific key. Set key Set() returns the key fetched from the map.

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What is HashTable?

Hashtable extends the Dictionary class and is synchronized. In binary search data structures can improve the efficiency of searches. The efficiency of search is increasing from O(n) to O(logn) by using binary search. Hash table is an example of a data structure. There are two parts of the hash table that is an array that is an actual table where data to be searched is stored and is called a mapping function. The second type is a hash function that is a mapping from the input space to the integer space that defines the indices of the array.

Key Differences

  1. HashMap implements the Map interface and is unsynchronized whereas Hashtable extends the Dictionary class and is synchronized.
  2. HashMap is unsynchronized whereas Hashtable is synchronized.
  3. HashMap cannot return Null value whereas Hashtable can return Null value.
  4. HashMap cannot be traverse directly whereas Hashtable can be traverse directly.

Comparison Video