Translate Java to T-SQL

void validateChecksum(String s)

    {

        StringBuffer stringbuffer = new StringBuffer();
        for(int i = 0; i < s.length(); i++)
        {
            if(s.charAt(i) <= '9' && s.charAt(i) >= '0')
            {
                stringbuffer.append(s.charAt(i));
            }
        }

        char ac[] = stringbuffer.toString().toCharArray();
        int j = 0;
        boolean flag = false;
        for(int k = ac.length - 1; k >= 0; k--)
        {
            if(flag)
            {
                int i1 = (ac[k] - 48) * 2;
                if(i1 > 9)
                {
                    j = j + 1 + (i1 - 10);
                } else
                {
                    j += i1;
                }
                flag = false;
            } else
            {
                j += ac[k] - 48;
                flag = true;
            }
        }

        int l = j % 10;
        if(l != 0)
        {
            
        } else
        {
            return;
        }
    }

DECLARE @MotiveCode varchar(20)
Set @MotiveCode = '0000000000000000'

Declare @CODE varchar(20)
DECLARE @i int, @j int, @tmp int, @flag varchar(10)

SELECT @i = 0
Select @j = 0
SELECT @tmp = 0
SELECT @flag = 'True'


WHILE (@j < LEN(@MotiveCode))
	BEGIN
		Select @j=@j+1
		IF @flag='True'
			BEGIN
				Select @tmp=ASCII(substring(@MotiveCode,@j-1,@j)-48)
				if(@tmp>9)
					BEGIN
						Select @i = @i+1+(@tmp - 10)	
						
					END
				ELSE
					BEGIN
						Select @i= @i+1
						
					
					END
				Select @flag = 'False'	
			END
		ELSE
			BEGIN
				Select @i = @i + substring(@MotiveCode,@j-1,@j)
				Select @flag = 'True'
			END
	
	END

Select @j % 10 as Result