SampleBatchWithState batch Apex

SampleBatchWithState.java

global class SampleBatchWithState implements Database.Batchable<sObject>, Database.Stateful {

  public Integer publicValue;
  private Integer privateValue;
  
  global SampleBatchWithState() {
    publicValue = 0;
    privateValue = 0;
  }

  // The batch job starts
  global Database.Querylocator start(Database.BatchableContext bc){
    String query = 'SELECT Id, Name FROM BatchData__c LIMIT 1000';
    return Database.getQuerylocator(query);
  } 
  
  // The batch job executes and operates on one batch of records
  global void execute(Database.BatchableContext bc, List<sObject> scope){
    System.debug('>>> execute start at ' + DateTime.now().format('yyyy/MM/dd hh:mm:ss'));
    // Reference https://www.xgeek.net/salesforce/a-way-to-make-thread-sleep-in-apex/
    Long startTime = DateTime.now().getTime();
    Long finishTime = DateTime.now().getTime();
    while ((finishTime - startTime) < 5000) {
      //sleep 5s
      finishTime = DateTime.now().getTime();
    }
    publicValue += 1;
    privateValue += 1;
    System.debug('>>> publicValue : ' + publicValue);
    System.debug('>>> privateValue : ' + privateValue);
    System.debug('>>> execute end at ' + DateTime.now().format('yyyy/MM/dd hh:mm:ss'));
  }
  
  // The batch job finishes
  global void finish(Database.BatchableContext bc){
    AsyncApexJob job = [SELECT Id, Status FROM AsyncApexJob WHERE Id = :bc.getJobId()]; 
    System.debug('>>>> finish ' + job.Status);
  }
}