Hi one account have multple related list project and case.prject and case open and closed activities iam showing account page.but i want all 3 list i want sort order.based on the due date i want sort order.please help me.

public class TicketsAndOpenActivitiesController{
    public List<case> theCase {get;set;}
    public List<Project__c> theProject {get;set;}
    public List<Account> theAccount {get; set;}
    public List<OpenActivity> openActivities {get;set;}
    public List<ActivityHistory> historyList {get;set;}
    public List<OpenActivity> finalOpenList {get;set;}
    public List<ActivityHistory> finalCloseList {get;set;}
    public Account acc;
    public case acc1;
    public Project__c acc2;
    
    public TicketsAndOpenActivitiesController(ApexPages.StandardController controller){
        openActivities = new List<OpenActivity>();
        historyList = new List<ActivityHistory>();
 this.acc=(Account)controller.getRecord();
        
        theAccount = [SELECT id,name,(SELECT id,Subject,ActivitySubtype, Owner.Name,WhoId,Who.Name,WhatId,What.Name,what.type,
                                   IsTask, ActivityDate, Status, Priority, OwnerId FROM OpenActivities Where What.type='Account' ORDER BY ActivityDate DESC),(SELECT id,Subject,ActivitySubtype, Owner.Name,WhoId,Who.Name,WhatId,What.Name,what.type,
                                    ActivityDate,IsTask, Status, Priority, OwnerId FROM activityhistories Where What.type='Account' ORDER BY ActivityDate DESC) 
                   From Account where Id=:acc.id];
        
       for(Account acc : theAccount){
            if(acc.OpenActivities.size() > 0){
                openActivities.addAll(acc.OpenActivities);
                
             }
        }
        for(Account acc : theAccount){
            if(acc.activityhistories.size() > 0){
                historyList.addAll(acc.activityhistories);
                
             }
        }
        
        theCase = [SELECT id,CaseNumber,Subject ,AccountId,(SELECT Subject,Id,ActivitySubtype, Owner.Name,WhoId,Who.Name,WhatId,What.Name,What.type,IsTask,ActivityDate, Status, Priority, OwnerId FROM OpenActivities where what.type='case' ORDER BY ActivityDate DESC),
                   (SELECT id,Subject,ActivitySubtype, Owner.Name,WhoId,Who.Name,WhatId,What.Name,what.type,
                                    ActivityDate,IsTask, Status, Priority, OwnerId FROM activityhistories Where What.type='case' ORDER BY ActivityDate DESC)  
                   FROM case where AccountId=:acc.id];
        
        for(Case c : theCase){
            if(c.OpenActivities.size() > 0){
                openActivities.addAll(c.OpenActivities);
            }
        }
        for(Case c : theCase){
            if(c.activityhistories.size() > 0){
                historyList.addAll(c.activityhistories);
                
             }
        }
        
        
        theProject = [SELECT id ,Customer__c,(SELECT Subject,Id,Owner.Name,WhoId,Who.Name,WhatId,ActivitySubtype,What.type,What.Name,IsTask, ActivityDate, Status, Priority, OwnerId FROM OpenActivities where what.type='Project__c' ORDER BY ActivityDate DESC) ,
                      (SELECT id,Subject,ActivitySubtype, Owner.Name,WhoId,Who.Name,WhatId,What.Name,what.type,
                                    ActivityDate,IsTask, Status, Priority, OwnerId FROM activityhistories Where What.type='Project__c' ORDER BY ActivityDate DESC)
                     FROM Project__c where Customer__c=:acc.id];  
     
        for(Project__c Project : theProject){
            if(Project.OpenActivities.size() > 0){
                openActivities.addAll(Project.OpenActivities);
            }
        }
        for(Project__c Project : theProject){
            if(Project.activityhistories.size() > 0){
                historyList.addAll(Project.activityhistories);
                
             }
        }
}
}