Answer 1

Do you want the substring between the two ones?

Edit:
If you want to find a substring which has as first and last number a 1 , you can create two int variables called indexFirst and IndexSecond then you call indexOf ('1') and assign it to indexFirst; After that you call indexOf('1', indexFirst + 1), the second argument is the index where it starts looking for the first argument. Then you assign this to indexSecond.The substring is String.substring (indexFirst, indexSecond + 1);