Yogesh's Tech Blog

As String is an immutable class , any update operations  like replace/substring/append is very expensive. As solution for this StringBuffer class has been introduced for all string update related operations. But problem with StringBuffer is that it is a synchronized class. All its public methods are tagged as “synchronized”. This adds an extra cost to string update operation whenever synchronized is actually not needed. As part of JDK 1.5 a new utility class called StringBuilder has been introduced for non-synchronized string update operations. StringBuilder is designed as a replacement for StringBuffer in single-threaded usage. It means using StrinBuilder instead of StringBuffer where ever synchronization is not an issue will be added to program performance.

      Please refer previous post for Singleton Designing Pattern . Concurrency is the one of the major issues with singleton designing pattern.       There will be multiple client accessing same singleton resource instance. If this resource is mutable then concurrency need to be taken care . Example from previous post is being used here. 1: package demo.singleton; 2: import java.util.concurrent.locks.ReadWriteLock; 3: import java.util.concurrent.locks.ReentrantReadWriteLock; 4: /** 5: * Singleton Resource Class 6: * @author Yogesh 7: */ 8: public class SingletonResource { 9: private static SingletonResource resorce = null ; 10: int count; 11: private ReadWriteLock writeLock = new ReentrantReadWriteLock(); 12: 13: public static SingletonResource getInstance(){ 14: if (resorce == null ){ 15: synchronized (SingletonResource. class ){ 16: if (res...

What is Atomic ? The term atomic is related to the atom, once considered the smallest possible unit. When computer code is considered atomic it can not be interrupted during its execution, We can also define atomic code as code that can’t be found in an intermediate state. Atomicity in Java - Java specifies that basic loading and storing of variable is the atomic. That means the value of the variable can’t be found in a interim state during the store not be changed in the middle of loading the variable to a register. Java Memory Model – Unfortunately , java’s memory model is a bit more complex. Threads are allowed to hold the values of variable in local memory. In that case, when one thread changes the values of the variable, another thread may not see the changed value. This is particularly in loops where looping is controlled by a variable. The lopping may be have already loaded the value of the variable into the register and does not necessary notice when another thread cha...