You should use Trigger.newMap instead of List as explained by Ralph in the answer.

In addition, to check the condition if the industry is changed or not there is an another Trigger context variable Trigger.oldMap where you can get previous value of field and this provide ability to compare the changes in record after update.

Ex:

for(Account acc : Trigger.newMap)
{
     Id oldvalue = Trigger.oldMap.get(acc.Id).Industry_Field__c;
     Id newValue = acc.Industry_Field__c;
     
     // check if industry field changed or not
     if(oldvalue != newValue )
     {
        // Proceed
     }
}

You should use Trigger.newMap instead of List as explained by Ralph in the answer.

In addition, to check the condition if the industry is changed or not there is an another Trigger context variable Trigger.oldMap where you can get previous value of field and this provide ability to compare the changes in record after update.

Ex:

for(Account acc : Trigger.newMap)
{
     Id oldvalue = Trigger.oldMap.get(acc.Id).Industry_Field__c;
     Id newValue = acc.Industry_Field__c;
     
     // check if industry field changed or not
     if(oldvalue != newValue )
     {
        // Proceed
     }
}

You should use Trigger.newMap instead of List as explained by Ralph in the answer.

In addition, to check the condition if the industry is changed or not there is an another Trigger context variable Trigger.oldMap where you can get previous value of field and this provide ability to compare the changes in record after update.

Ex:

for(Account acc : Trigger.newMap)
{
     Id oldvalue = Trigger.newMap.get(acc.Id).Industry_Field__c;
     Id newValue = acc.Industry_Field__c;
     
     // check if industry field changed or not
     if(oldvalue != newValue )
     {
        // Proceed
     }
}

You should use Trigger.newMap instead of List as explained by Ralph in the answer.

In addition, to check the condition if the industry is changed or not there is an another Trigger context variable Trigger.oldMap where you can get previous value of field and this provide ability to compare the changes in record after update.

Ex:

for(Account acc : Trigger.newMap)
{
     Id oldvalue = Trigger.oldMap.get(acc.Id).Industry_Field__c;
     Id newValue = acc.Industry_Field__c;
     
     // check if industry field changed or not
     if(oldvalue != newValue )
     {
        // Proceed
     }
}