Map<String,Schema.SObjectType> gd = Schema.getGlobalDescribe();
Schema.DescribeSObjectResult r = gd.get(':::Put Your Object here:::').getDescribe();
Map<String,Schema.SObjectField> M = r.fields.getMap();
for(String fieldName : M.keySet()) {
    Schema.SObjectField field = M.get(fieldName);
    Schema.DescribeFieldResult F = field.getDescribe();
    //A nillable field can have empty content.
    //A isNillable Boolean non-nillable field must have a value for the object to be created or saved.
    // if F.isNillable() is false then field is mandatory
    Boolean isFieldreq  = F.isNillable();

    system.debug('field-->'+F.getName()+': isMandatory-->'+!isFieldreq);
}