check if string has substring code example

Example 1: if str contains jquery

if (str.indexOf("Yes") >= 0)
  
  //case insensitive version
  if (str.toLowerCase().indexOf("yes") >= 0)

Example 2: check if string contains substring sql

Declare @mainString nvarchar(100)='Amit Kumar Yadav'  
---Check here @mainString contains Amit or not, if it contains then retrun greater than 0 then print Find otherwise Not Find  
if CHARINDEX('Amit',@mainString) > 0   
begin  
   select 'Find' As Result  
end  
else  
    select 'Not Find' As Result

Example 3: how to check if a string contains a character

public static boolean containsIgnoreCase(String str, char c) {
        str = str.toLowerCase();

        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == Character.toLowerCase(c)) {
                return true;
            }
        }
        
        return false;
    }