ConcurrentHashMap in Java

ConcurrentHashMap is an alternative to HashTable and synchronizedMap. It is used in multi threaded applications and provided better performance when compared to HashTable and synchronisedMap. ConcurrentHashMap Implementation In Java In concurrentHashMap we have new feature called concurrency level . The ConcurrentHashMap is divided into segments based on the concurrency level.We need to be careful while […]

Fail fast & Fail safe Iterators in Java

Iterators are basically used to traverse over a set of objects one by one. Java supports two types of Iterators  Fail Fast Iterator Fail Safe Iterator Fail Fast Iterator Fail fast iterator do not allow any modifications to a collection while iterating/traversing the collection.By modification I mean any updating, addition of elements in the collection.If […]

Equals() and hashCode() method in Java

Object Equality When it comes to Java ,there are two types of Object equality ,reference equality and object equality. Reference Equality Two references that refer to the same object on the heap are considered equal.If you want to check if two references are referring to the same object using the ‘==’ operator. The ‘==’ operator […]

How HashMap works in Java1.8?

HashMap is a hash table implementation of Map interface in Java. A map contains a collection of key-value pairs where key maps to the value.HashMap permits null values and null keys and it doesn’t permit duplicate keys.It is unordered so it doesn’t guarantee that the order will remain constant with time. Hashmap provides constant time […]

How to resolve package com.sun.image.codec.jpeg does not exist?

Sometimes the java project (usually a lower version of Java (1.6 or lower)) results in the following compilation error:- INFO] Compiling 106 source files to /Users/JavaProject/src/java/web/target/classes [INFO] ————————————————————- [ERROR] COMPILATION ERROR : [INFO] ————————————————————- [ERROR] /Users/JavaProject//src/java/web/main/java/net/esi/ppc/presentation/service/CaptchaImageGenerator.java:[24,31] error: package com.sun.image.codec.jpeg does not exist [ERROR] /Users/JavaProject//src/java/web/main/java/net/esi/ppc/presentation/service/CaptchaImageGenerator.java:[25,31] error: package com.sun.image.codec.jpeg does not exist To resolve this issue you […]