Automatically schedule a batch from finish method

The below Batch Apex will schedule the class to run for every 1 minute and will also a send an email about batch status in Finish method of this class

global class contactBatch implements Database.Batchable<sObject> {

global Database.QueryLocator start(Database.BatchableContext BC) {
String query = 'SELECT Id,Name FROM Contact';
return Database.getQueryLocator(query);
}

global void execute(Database.BatchableContext BC, List<Contact> scope) {
for(contact a : scope)
{
a.Phone = '+91-8428575275';
}
update scope;
}

global void finish(Database.BatchableContext BC) {

Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();

//Below code will fetch the job Id
AsyncApexJob a = [Select a.TotalJobItems, a.Status, a.NumberOfErrors, a.JobType, a.JobItemsProcessed, a.ExtendedStatus, a.CreatedById, a.CompletedDate From AsyncApexJob a WHERE id = :BC.getJobId()];//get the job Id

if(a.Status == 'Completed')
{

List<CronTrigger> scheduledJobs = [Select id from cronTrigger where CronJobDetail.name = 'Scheduler'];

if(scheduledJobs.isEmpty())
{
Decimal minutes=1;
Decimal chunkSize=200;
Boolean isChaining=true;

if(isChaining)
System.scheduleBatch(new contactBatch(),'Scheduler',minutes.intValue(),chunkSize.intValue());
}
}

//below code will send an email to User about the status
String[] email = new String[]{'din2262@gmail.com'};
mail.setToAddresses(email);
mail.setReplyTo('din2262@gmail.com');//Add here your email address
mail.setSenderDisplayName('Apex Batch Processing ');
mail.setSubject('Batch Processing '+a.Status);
mail.setPlainTextBody('The Batch Apex job processed '+a.TotalJobItems+'batches with '+a.NumberOfErrors+'failures'+'Job Item processed are'+a.JobItemsProcessed);

Messaging.sendEmail(new Messaging.SingleEmailmessage [] {mail});
}
}