虽然可以用换行符把很长的字符串放在一行，但是不便于阅读。apex没有像python中三个引号这种直接支持多行字符串的格式，可以用下面这种方法：

String query = 'SELECT Project__c,'+ ' Project__r.Testing_Submitted__c,'+ ' Project__r.Project_Sub_Phase__c,'+ ' Project__r.DRD_Submited__c,'+ ' Protected_Application__r.DRD_Completed__c,'+ ' Protected_Application__c,'+ ' Project__r.Id,'+ ' Project__r.Name,'+ ' Project__r.Project_Type__c,'+ ' Project__r.Remark__c,'+ ' Project__r.Record_Type_Name__c,'+ ' Project__r.RecordTypeId,'+ ' Project__r.Project_Actual_Completion__c,'+ ' Protected_Application__r.Application__c,'+ ' Project__r.Project_Phase__c,'+ ' Project__r.Ready_for_Testing__c,'+ ' Project__r.recordType.DeveloperName,'+ ' Project__r.Project_Sub_Status__c,'+ ' Project__r.Certification_was_submitted__c,'+ ' Project__r.Customer_confirmed_launch_date__c,'+ ' Protected_Application__r.Application_Type__c'+ ' FROM ProjectAppLink__c ';System.debug(query);

参考：https://salesforce.stackexchange.com/questions/150674/break-line-on-a-string