Difference Betwixt Arraylist As Well As Hashmap Inwards Java

Difference betwixt ArrayList together with HashMap inwards Java
One of the most critical departure betwixt HashMap together with ArrayList shape is that onetime is the implementation of the hash tabular array spell after is a dynamic array which tin resize itself. The HashMap together with ArrayList are 2 of the most pop classes from Java Collection framework. Though both are used to shop objects but they are completely dissimilar on their implementation, working together with usage. The master copy departure betwixt ArrayList together with HashMap is that ArrayList is index based data-structure backed yesteryear an array spell HashMap is map information construction which plant on hashing to recall stored values. This is likewise 1 of the oft asked Java Collection interview questions, which is often asked Java developers of 1 to iii years of experience. Apart from this telephone substitution departure betwixt ArrayList together with HashMap, in that place are many other differences, which nosotros volition encounter inwards this Java tutorial. But earlier that let's encounter roughly similarity betwixt ArrayList together with HashMap inwards Java.

Similarity betwixt ArrayList together with HashMap inwards Java

Here are roughly of the most mutual similarities betwixt ArrayList together with HashMap inwards Java:

1) BothArrayList together with HashMap are non synchronized, y'all should non occupation them inwards the multi-threading surroundings without external  synchronization.

2) Both ArrayList together with HashMap Iterator are fail-fast, they volition throw ConcurrentModificationException every bit presently every bit they honour whatsoever structural alter inwards ArrayList or HashMap 1 time Iterator is created.

3) Both ArrayList together with HashMap allows null. HashMap allows cypher key together with values.

4) ArrayList allows duplicate elements together with HashMap allow duplicate values.

5) In damage of performanceArrayList get() render constant fourth dimension surgical operation if y'all know index similar to get() method of HashMap which provides constant-time performance.

6) ArrayList is backed yesteryear array similarly, HashMap is likewise internally implemented yesteryear Array.

7) Both ArrayList together with HashMap tin last traversed through Iterator inwards Java.


Here is a squeamish summary of similarity betwixt ArrayList together with HashMap inwards Java:

Difference betwixt ArrayList vs HashMap inwards Java

Now it's fourth dimension to encounter crucial differences betwixt ArrayList vs HashMap inwards Java. This volition tending y'all to hit upward one's heed which Collection shape is appropriate for a item occupation case:

1) The outset departure betwixt ArrayList  together with HashMap is that ArrayList implements List interface spell HashMap implements Map interface inwards Java. See the difference betwixt listing together with map for to a greater extent than information. 

2) The minute departure betwixt ArrayList together with HashMap is that ArrayList exclusively stores 1 object spell HashMap stores 2 objects key together with value.

3) The tertiary departure betwixt HashMap together with ArrayList is that, keys of HashMap must implements equals together with hashCode method correctly, ArrayList doesn't accept that requirement but its proficient to accept that because contains()  method of ArrayList volition occupation equals() method to encounter if that object already exists or not.

4) The quaternary departure betwixt HashMap together with ArrayList is that ArrayList maintains the social club of object, inwards which they are inserted spell HashMap doesn't render whatsoever ordering guarantee.

5) Another departure betwixt ArrayList together with HashMap is that ArrayList allows duplicates but HashMap doesn't allow duplicates key though it allows duplicate values.

6) ArrayList get(index) method e'er gives an O(1) surgical operation but HashMap get(key) tin last O(1) inwards the best illustration together with O(n) inwards the worst case.

Here is a squeamish slide which highlights they key departure betwixt ArrayList together with HashMap inwards Java:

That's all almost the difference betwixt ArrayList together with HashMap in Java. They both are completely dissimilar to each other together with be for a dissimilar purpose.Use HashMap if y'all demand map form of construction to map keys to values together with occupation ArrayList if y'all simply looking to shop objects inwards Java.

Related Java Collections Interview Questions

• The departure betwixt HashSet together with TreeSet inwards Java? (answer)
• The departure betwixt ArrayList together with HashSet inwards Java? (answer)
• The departure betwixt Hashtable together with HashMap inwards Java? (answer)
• The departure betwixt HashMap together with LinkedHashMap inwards Java? (answer)
• The departure betwixt ConcurrentHashMap together with HashMap inwards Java? (answer)
• The departure betwixt ArrayList together with Vector inwards Java? (answer)
• The departure betwixt ArrayList together with LinkedList inwards Java? (answer)

Further Learning
Java In-Depth: Become a Complete Java Engineer
Java Fundamentals: Collections
Data Structures together with Algorithms: Deep Dive Using Java