Apex - do-while Loop


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Unlike the for and the while loops which test the loop condition at the top of the loop, the do...while loop checks its condition at the bottom of the loop.

A do...while loop is similar to a while loop, except that a do...while loop is guaranteed to execute at least one time.

Syntax

do { code_to_execute } while (Boolean_condition);

Flow Diagram

Apex do-while Loop

Example

For our Chemical Company, we will be updating the only first 1 record in List, not more than that.

// Code for do while loop
List<apex_invoice__c> InvoiceList = [SELECT Id, APEX_Description__c,
   APEX_Status__c FROM APEX_Invoice__c LIMIT 20];  //it will fetch only 20 records

Integer i = 0;
do {
   InvoiceList[i].APEX_Description__c = 'This is the '+i+' Invoice';
   
   // This will print the updated description in debug log
   System.debug('****Updated Description'+InvoiceList[i].APEX_Description__c);
   i++; // Increment the counter
} while (i< 1);   // iterate till 1st record only
apex_loops.htm
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