Schedule the batch class for every 1 hour.

At first we should write a Batch class without a schedule code in it.

create the below schedule class.

Schedule Class

global class ScheduleClass implements Schedulable {
   global void execute(SchedulableContext sc) {
      BatchClass  b = new BatchClass(); 
      database.executebatch(b);
   }
}

After saving that schedule class append the code which I have highlighted in red color in finish method of batch Apex.

Batch Class

global class BatchClass implements Database.Batchable<sobject>
{
        global Database.QueryLocator start(Database.BatchableContext BC){
             String Query='Select LastName,Id from Lead';
              return Database.getQueryLocator(Query);
        }
        global void Execute(Database.BatchableContext BC,List<sobject> Scope){
                List<Lead> ld = Scope;
                for(Lead l: ld){
                        l.LastName = l.LastName+'Batch testing';
               }

       }
       global void finish(Database.BatchableContext BC){
              Datetime sysTime = System.now();
              sysTime = sysTime.addMinutes(60);
              String chron_exp = '' + sysTime.second() + ' ' + sysTime.minute() + ' ' + 

              sysTime.hour() + ' ' + sysTime.day() + ' ' + sysTime.month() + ' ? ' + sysTime.year();
              system.debug(chron_exp);
              ScheduleClass ssr = new ScheduleClass();  // Schedule class name
              String sch = 'Schedulejob' + chron_exp;
              List<AsyncApexJob> aaj = [select ApexClassID,CompletedDate,ExtendedStatus,

                                                                       JobItemsProcessed,JobType,MethodName, 

                                                                       NumberOfErrors,Status,TotalJobItems 

                                                                      from AsyncApexJob

                                                                      where status='queued'];
              if(aaj.size()== 0){
                   system.schedule(sch,chron_exp,ssr); 
              }

       }
}

The chron_exp will used to schedule the class for every 1 hour based on the System Time.

we need to execute the above code as a anonymous using developer console.

Once it has been started to execute, it will automatically schedule the apex class for every 1 hour.