Salesforce Asynchronous process in one place

Program-1:Calling Future method from Batch apex

Global class MassDeleteBatch implements Database.Batchable<sobject>
{
   //Calling @future method from Constructor 
    global MassDeleteBatch()
    {       
        fuMethod1();   
 fuMethod2();
 //We can call upto 50 future methods 
    }
    global Database.QueryLocator start(Database.BatchableContext BC)
    {
        return Database.getQueryLocator([Select Id from Account]);
    }
    global void execute(Database.BatchableContext BC, List<SObject> lstRecords)
    {
  //Your business logic goes here 
    }
    global void finish(Database.BatchableContext BC) { }
    
    @future(callout=true)
    public static void fuMethod1()
    {
        //Callout logic inside the @future method'
    }
 @future
    public static void fuMethod2()
    {
        //Your logic inside the @future method'
    }
}

Note: Only thing is we can't call @future method from start(), execute(),finish() methods. If we do then we will get the "First error: Too many future calls: 1" error.
Program-2: Calling Batch class from Future Method

Global class BatchExample implements Database.Batchable<sobject>
{ 
    global Database.QueryLocator start(Database.BatchableContext BC)
    {        
        return Database.getQueryLocator([Select Id from Account]);
    }
    global void execute(Database.BatchableContext BC, List<SObject> lstRecords)
    {  
  //batch logic here
    }
    global void finish(Database.BatchableContext BC) { 
 }   
}
//-----------------------------------------------
public class BaseClass 
{
    @future
    public static void toCallBatchClass()
    {
        Database.executeBatch(new MassDeleteBatch());
    }
}

//----------Executing From Anonymous Window--------------
BaseClass.toCallBatchClass();

The above program will throw the below error :

First error: Database.executeBatch cannot be
called from a batch start, batch execute, or future method.

Program-3:Calling Future method from Future method

public class BaseClass 
{
    @future
    public static void toCallAnotherFuture()
    {
        futureMethod();
    }
    @future
    public static void futureMethod()
    {
        //Your logic here
    }
}

//----------Executing From Anonymous Window--------------
BaseClass.toCallAnotherFuture();

The above program will throw the below error :

First error: Future method cannot be called
from a future or batch method: BaseClass.futureMethod()

Program-4:Calling Queueable class from Future method

public class BaseClass 
{
    @future
    public static void toCallQueueableClass()
    {
       System.enqueueJob(new QblClass());
    }    
}
//-----------------------------------------------
public class QblClass  implements Queueable {
    public void execute(QueueableContext context)
    {
    }
}

//----------Executing From Anonymous Window--------------
BaseClass.toCallQueueableClass();

Program-5: Calling Batch apex from Queueable Class

public class QblClass  implements Queueable {
    public void execute(QueueableContext context)
    {
        Database.executeBatch(new BatchExample());
    }
}
//-----------------------------------------------
Global class BatchExample implements Database.Batchable<sobject>
{ 
    global Database.QueryLocator start(Database.BatchableContext BC)
    {        
        return Database.getQueryLocator([Select Id from Account]);
    }
    global void execute(Database.BatchableContext BC, List<SObject> lstRecords)
    {  
  //batch logic here
    }
    global void finish(Database.BatchableContext BC) { 
 }   
}
//----------Executing From Anonymous Window--------------
System.enqueueJob(new QblClass());

Program-6: Calling Future method from Queueable Class

public class QblClass  implements Queueable {
    public void execute(QueueableContext context)
    {
       toCallQueueableClass();
    }
    @future
    public static void toCallQueueableClass()
    {
       
    }    
}
//----------Executing From Anonymous Window--------------
System.enqueueJob(new QblClass());

 tHiNk gooD and dO thE bEsT.........MANJU NATH 🌝