Match two Sobject field API Names and put the common in a Set

Question

I am trying to pass two Sobject names to a method and match using Schema the Field API Names common in both of them.

Like I have Object1 having fields A__c, B__c,X__c. Object2 having fields A__c, B__c,Y__c.

Here A__c and B__c are the matching fields. Now I need to put these field names in a Set which will have values 'A__c' , 'B__c'.

Can someone please help me to find out how to compare between two Schema.DescribefieldResult?

Apex code:

public static String Compare(String str, String str1)
    {
              String sObjectName = str;
              String sObjectName1 = str1;
        System.debug('=========  '+ sObjectName);
        List<Schema.SObjectField> sss=new list<Schema.SObjectField>();

        if(sObjectName != null && sObjectName != '' )

        Schema.SObjectType gd = Schema.getGlobalDescribe().get(sObjectName); 
        Schema.DescribeSobjectResult a11=gd.getDescribe();
        Map<String, Schema.SObjectField> M = a11.fields.getMap();        
        for(Schema.SObjectField s1:m.values()){                            
            Schema.DescribeFieldResult f = M.get(s1.getDescribe().getName()).getDescribe();

        Schema.SObjectType gd1 = Schema.getGlobalDescribe().get(sObjectName1); 
        Schema.DescribeSobjectResult a=gd1.getDescribe();
        Map<String, Schema.SObjectField> M1 = a.fields.getMap();        
        for(Schema.SObjectField s2:m1.values()){                            
            Schema.DescribeFieldResult f2 = M2.get(s2.getDescribe().getName()).getDescribe();
        }
    }

Answer 1

Try this:

public static String Compare(String str, String str1){

    String sObjectName = str;
    String sObjectName1 = str1;
    List<String> fieldsS1 = new list<String>();
    List<String> fieldsS2 = new list<String>();
    for(Schema.SObjectField s1:Schema.getGlobalDescribe().get(sObjectName).getDescribe().fields.getMap().values()){      
        //get Fields of First object                     
        fieldsS1.add(s1.getDescribe().getName());

  }
    for(Schema.SObjectField s1:Schema.getGlobalDescribe().get(sObjectName1).getDescribe().fields.getMap().values()){    
        //get Fields of Second object                         
        fieldsS2.add(s1.getDescribe().getName());

  }

    Set<String> uniquefieldsS1 = new Set<String>(fieldsS1);
    List<String> uniqueFields = new List<String>();
    for(String str: fieldsS1){
        if(uniquefieldsS2.contains(str)){
            uniqueFields.add(str);
        } 
    }
}

uniqueFields is the Set which contains the Unique fields.