How to lock state to synchonize transitions java android

Hi there!
Today i'm gonna share one of many possible ways to acquire a lock with the intent of synchronize transitions or whatever task you may have. I use it to synchronize complex animation transition sequences in Android.

import java.util.HashSet;
import java.util.Set;

/**
 * Use this class to synchronize transitions, animations or whatever you want.

 * It is designed to acquire and release a synchronized lock state, coordinating

 * the access of it in a multi thread environment.
 * 
 * @author Ricardo Ferreira 04/11/2013
 */
public class StateLock {

 private final static StateLock INSTANCE = new StateLock();
 private Set lockSet = new HashSet();
 private boolean lock = false;
 
 private StateLock() {
  // singleton
 }

 /** Synchronized because the lock state should be acquired and released in a controlled way */
 public synchronized static StateLock getInstance() {
  return StateLock.INSTANCE;
 }

 public synchronized boolean isStateLocked() {
  return lock;
 }
 
 public synchronized boolean hasStateAlreadyLocked(String stateSimpleClassName) {
  return lockSet.contains(stateSimpleClassName);
 }

 /** Returns true if the state lock was acquired by the given class, false otherwise */
 public synchronized boolean acquireLockState(String stateSimpleClassName) {
  boolean operationResult = false;
  if (lockSet.isEmpty()) {
   lockSet.add(stateSimpleClassName);
   lock = true;
   operationResult = true;
  }
  return operationResult;
 }

 /** Returns true if the lock was released or no state was locked, false otherwise */
 public synchronized boolean releaseLockState(String stateSimpleClassName) {
  boolean operationResult = false;
  if (lockSet.contains(stateSimpleClassName)) {
   lockSet.clear();
   lock = false;
   operationResult = true;
  } else if (lockSet.isEmpty()) {
   lock = false;
   operationResult = true;
  }
  return operationResult;
 }

 protected Object clone() throws CloneNotSupportedException {
  throw new CloneNotSupportedException();
 }

}

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How to write a singleton? (pros and contras)

A singleton for each situation and the pros and contras of it?


Lazy synchronized initialization

public final class Session 
  {
      private static Session instance;
 
      /** singleton */
      private Session() {}
 
      /** if you do not need synchronisation do not mark it as synchronized */
      public synchronized static Session getInstance() 
      {
          return (instance == null) ? instance = new Session() : instance;
      }
      /** your methods goes here... */
   }

PRO: can be initialized lazy the first time it is used
CONTRA: Singletons shall be avoid because they are hard to test and debug. Futher they contribute to less cohesive designs.


No Lazy initialization needed

public class Session 
  {
    private final static Session INSTANCE = new Session();

    private Session() {}

    public static Session getInstance() 
    { 
      return Session.INSTANCE; 
    }

    protected Object clone() 
    {
      throw new CloneNotSupportedException();
    }

    /** your methods goes here... */
  }

PRO: Immediate allocation of the needed resource
CONTRA: Needs "more" resource as nescessary + CONTRA from first case


No Lazy initialization needed (the elegant, modern way)

public enum Session 
   {
       INSTANCE;
       private int session;

       public int getSession() {
           return ++session;
       }

       /** your methods goes here... */
   }

PRO: Very simple, modern way. Immediate allocation of the needed resource
CONTRA: Needs "more" resource as nescessary + CONTRA from first case

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Be sure to read, it will change your life!

Show your work by Austin Kleon: https://amzn.to/34NVmwx

This book is a must read - it will put you in another level! (Expert)

Agile Software Development, Principles, Patterns, and Practices: https://amzn.to/30WQSm2

Write cleaner code and stand out!

Clean Code - A Handbook of Agile Software Craftsmanship: https://amzn.to/33RvaSv

This book is very practical, straightforward and to the point! Worth every penny!

Kotlin for Android App Development (Developer's Library): https://amzn.to/33VZ6gp

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