Java Collections supports 2 types of Iterator, neglect prophylactic in addition to neglect fast. The primary distinction betwixt a fail-fast in addition to fail-safe Iterator is whether or non the underlying collection tin endure modified land its get iterated. If y'all accept used Collection similar ArrayList thence y'all know that when y'all iterate over them, no other thread should modify the collection. If Iterator detects whatever structural alter subsequently iteration has begun e.g adding or removing a novel chemical gene thence it throws ConcurrentModificationException, this is known every bit fail-fast deportment in addition to these iterators are called fail-fast iterator because they neglect every bit before long every bit they notice whatever modification . Though it's non necessary that iterator volition throw this exception when multiple threads modified it simultaneously. it tin come about fifty-fifty alongside the unmarried thread when y'all effort to take elements by using ArrayList's remove() method instead of Iterator's take method, every bit discussed inwards my before post, 2 ways to take objects from ArrayList.
Most of the Collection classes from Java 1.4 e.g. Vector, ArrayList, HashMap, HashSet has fail-fast iterators. The other type of iterator was introduced inwards Java 1.5 when concurrent collection classes e.g. ConcurrentHashMap, CopyOnWriteArrayList in addition to CopyOnWriteArraySet was introduced.
These iterator uses a stance of master copy collection for doing iteration in addition to that's why they doesn't throw ConcurrentModificationException fifty-fifty when master copy collection was modified subsequently iteration has begun. This agency y'all could iterate in addition to operate alongside stale value, but this is the toll y'all require to pay for fail-safe iterator in addition to this characteristic is clearly documented
1) Fail-fast Iterator throws ConcurrentModfiicationException every bit before long every bit they notice whatever structural alter inwards collection during iteration, basically which changes the modCount variable agree past times Iterator. While fail-fast iterator doesn't throw CME.
You tin likewise run across Core Java Volume 1 - Fundamentals past times Cay S. Horstmann to larn to a greater extent than well-nigh how to purpose Iterator in addition to properties of unlike types of iterators inwards Java.
2) Fail-fast iterator traverse over master copy collection course of written report land fail-safe iterator traverse over a re-create or stance of master copy collection. That's why they don't notice whatever alter on master copy collection classes in addition to this likewise agency that y'all could operate alongside stale value.
3) Iterators from Java 1.4 Collection classes e.g. ArrayList, HashSet in addition to Vector are fail-fast land Iterators returned past times concurrent collection classes e.g. CopyOnWriteArrayList or CopyOnWriteArraySet are fail-safe.
4) Iterator returned past times synchronized Collection are fail-fast land iterator returned past times concurrent collections are fail-safe inwards Java.
5) Fail fast iterator plant inwards alive information but choke invalid when information is modified land fail-safe iterator are weekly consistent.
That's all well-nigh difference betwixt fail-safe in addition to fail-fast iterator inwards Java. Now y'all know that its merely tow kinds of iterator which send differently when underlying collection course of written report is modified past times adding or removing whatever object. Keep inwards hear that when y'all operate alongside concurrent collection classes similar ConcurrentHashMap y'all operate alongside fail-safe iterator, which volition non throw ConcurrentModificationException but non necessarily endure belongings the most updated stance of underlying Collection.
If y'all similar this article in addition to hungry for to a greater extent than Interview questions from Java Collection framework thence delight banking concern lucifer next articles from this spider web log :
Most of the Collection classes from Java 1.4 e.g. Vector, ArrayList, HashMap, HashSet has fail-fast iterators. The other type of iterator was introduced inwards Java 1.5 when concurrent collection classes e.g. ConcurrentHashMap, CopyOnWriteArrayList in addition to CopyOnWriteArraySet was introduced.
These iterator uses a stance of master copy collection for doing iteration in addition to that's why they doesn't throw ConcurrentModificationException fifty-fifty when master copy collection was modified subsequently iteration has begun. This agency y'all could iterate in addition to operate alongside stale value, but this is the toll y'all require to pay for fail-safe iterator in addition to this characteristic is clearly documented
Difference betwixt Fail Safe in addition to Fail Fast Iterator inwards Java
In lodge to best empathise divergence betwixt these 2 iterator y'all require to effort out examples alongside both traditional collections similar ArrayList in addition to concurrent collections similar CopyOnWriteArrayList. Nevertheless let's showtime run across roughly telephone substitution differences ane at a fourth dimension :1) Fail-fast Iterator throws ConcurrentModfiicationException every bit before long every bit they notice whatever structural alter inwards collection during iteration, basically which changes the modCount variable agree past times Iterator. While fail-fast iterator doesn't throw CME.
You tin likewise run across Core Java Volume 1 - Fundamentals past times Cay S. Horstmann to larn to a greater extent than well-nigh how to purpose Iterator in addition to properties of unlike types of iterators inwards Java.
2) Fail-fast iterator traverse over master copy collection course of written report land fail-safe iterator traverse over a re-create or stance of master copy collection. That's why they don't notice whatever alter on master copy collection classes in addition to this likewise agency that y'all could operate alongside stale value.
3) Iterators from Java 1.4 Collection classes e.g. ArrayList, HashSet in addition to Vector are fail-fast land Iterators returned past times concurrent collection classes e.g. CopyOnWriteArrayList or CopyOnWriteArraySet are fail-safe.
4) Iterator returned past times synchronized Collection are fail-fast land iterator returned past times concurrent collections are fail-safe inwards Java.
5) Fail fast iterator plant inwards alive information but choke invalid when information is modified land fail-safe iterator are weekly consistent.
When to purpose neglect fast in addition to fail-safe Iterator
Use fail-safe iterator when y'all are non bothered well-nigh Collection to endure modified during iteration, every bit fail-fast iterator volition non allow that. Unfortunate y'all can't lead neglect prophylactic or fail-fast iterator, it depends on upon which Collection course of written report y'all are using. Most of the JDK 1.4 Collections e.g. HashSet, Vector, ArrayList has fail-fast Iterator in addition to exclusively Concurrent Collections introduced inwards JDK 1.5 e.g. CopyOnWriteArrayList in addition to CopyOnWriteArraySet supports neglect prophylactic Iteration. Also, if y'all desire to take elements during iteration delight purpose iterator's remove() method in addition to don't purpose take method provided past times Collection classes e.g. ArrayList or HashSet because that volition effect inwards ConcurrentModificationException.
That's all well-nigh difference betwixt fail-safe in addition to fail-fast iterator inwards Java. Now y'all know that its merely tow kinds of iterator which send differently when underlying collection course of written report is modified past times adding or removing whatever object. Keep inwards hear that when y'all operate alongside concurrent collection classes similar ConcurrentHashMap y'all operate alongside fail-safe iterator, which volition non throw ConcurrentModificationException but non necessarily endure belongings the most updated stance of underlying Collection.
If y'all similar this article in addition to hungry for to a greater extent than Interview questions from Java Collection framework thence delight banking concern lucifer next articles from this spider web log :
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