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  Java AbstractMethodError explained and demonstrated

According to Oracle Java API documentation, AbstractMethodError is a kind of runtime error where the application is having some incompatible changes which leads to a missing implementation of an abstract method. Below is the official description. Thrown when an application tries to call an abstract method. Normally, this error is caught by the compiler; this error can only occur at run time if the definition of some class has incompatibly changed since the currently executing method was last co...

   JAVA,ABSTRACTMETHODERROR     2016-07-22 22:03:20

  9 Ways to Create Thread Pools with Java Executors

In Java, the Executors class provides a variety of static factory methods to create different types of thread pools. When learning about thread pools, the Executors class is indispensable. Mastering its usage, principles, and scenarios will enable you to apply it smoothly in actual project development. Here are some commonly used methods, which I will explain one by one: newCachedThreadPool(): Creates a cached thread pool. If a thread has not been used for 60 seconds, it will be terminated and ...

   TUTORIAL,JAVA THREAD     2024-07-19 23:07:09

  Comparable and comparator in Java

Comparable and comparator are two similar interfaces used to compare objects in Java. When we want to sort a list of objects such as Employee or User etc, we may need to implement these interfaces to make them comparable as we want. However, there are some differences between comparable and comparator interface.ComparableA comparable object is capable of comparing itself with another object. The class itself must implements the java.lang.Comparable interface in order to be able to compare its in...

   Java,Comparable,Comparator,Sort     2012-07-04 12:06:15

  Why exception would be thrown when deleting element while looping through HashMap in Java

HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List. Below is a sample code snippet demonstrating the exception thrown. Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1"); map.put("ke...

   JAVA,HASHMAP,CONCURRENTMODIFICATIONEXCEPTION     2018-06-30 12:49:09

  How expensive is a MySQL query?

Database access speed is always the bottle neck of many applications. Many application have large amount of data to search, retrieve and display nowadays. How do we improve the performance of our applications, how do we reduce the cost of database access? Apart from the design of database, the quality of the query is also one important factor to take care.  But before that, we need to know how much network traffic a query will consume. Yunyang,Zhang from Nubee in Singapore did some research...

   MySQL,Network traffic,Query     2013-04-09 05:13:33

  Arrays.equals() vs MessageDigest.isEqual()

Both Arrays.equals() and MessageDigest.isEqual() are used to compare the equality of two arrays. They can be interchangeably in many cases. However, they do have some differences which lead to different use cases in real applications. One difference is that the arrays passed to MessageDigest.isEqual() cannot be null while it's ok for Arrays.equals(). The one major difference between these two methods is that Arrays.equals() is not time-constant while MessageDigest.isEqual() is time-constant. Thi...

   Arrays.equal(),MessageDigest.isEqual(),Java,Security     2015-05-14 22:03:29

  Deep Understanding of ReentrantLock: Unlocking the Mysteries of Java Concurrent Programming

ReentrantLock introduction ReentrantLock is a class in the Java concurrent package, java.util.concurrent.locks, and is an implementation of the Lock interface. As its name suggests, it is a reentrant mutual exclusion lock. A mutual exclusion lock is a synchronization tool used to protect shared resources, ensuring that only one thread can access the resource at a given time. Reentrant means that a thread can acquire the same lock multiple times without causing a deadlock. This lock provides some...

   JAVA,REENTRANTLOCK,CONCURRENCY,MULTITHREADING     2023-05-22 08:01:13

  NIO vs IO in Java

Java 1.4 provides a new API for handling IO -- NIO. This is a non-blocking and buffer oriented IO API. Below are main differences between the NIO and IO in Java. IO NIO Stream oriented Buffer oriented Blocking IO Non-blocking IO N/A Using selector Stream oriented vs Buffer oriented The main difference is that IO is stream oriented where the data is read byte by byte and the data will not be buffered normally.This means there is no pointer to move forward and backward in the stream. I...

   JAVA,IO,NIO     2016-01-10 01:40:02

  Inline IF and CASE statements in MySQL

There are times where running IF statements inside a query can be useful. MySQL provides a simple way to do this through the use of IF and CASE statements. The IF statement takes three arguments; the conditional, the true value and the false value. False and true values may be static values or column values. For example: SELECT IF(score > 100, 100, score) AS score FROM exam_results this will return the value in the score column limited to a maximum value of 100. IF statements can a...

   MySQK,IF,Condition,CASE,SQL     2012-04-22 10:37:01

  Launch Java process programmatically in Java

In some cases while working on some automation testcase, developers would like to launch Java process programmatically so that the tests can be ran without manual intervention. Java provides such methods to achieve this. ProcessBuilder can be used to build a Java process which can be launched when everything is ready. Basically it can take a list of parameters which are similar to the command line options/arguments.  For example, if you want to launch a Java process, you can do followi...

   JAVA,PROCESSBUILDER,COMMAND LINE     2016-04-27 04:03:30

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