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Reading a String backward

G. Graz
Ranch Hand

Joined: Oct 23, 2006
Posts: 30
In my very last method ( int BTD) I am trying to read a string input form right to left when the input for the integer starts with one ( in this case a negative number , since I am testing for binary ) . Basically I am doing the � Two�s Complement� method on the negative number turn it into a positive binary number and just add the �-� negative sign in front of it , something like ( result = �-� + result ) . So I have no problem taking the positive binary number and converting to decimal , but can not figure out the correct way to code the negative number block of code ? Please any suggestions would be of great help !! listed below is my code , it attaches to a user class that gets the I/O but my professor did not give us access to that code . Thank you everyone for the insight !

Campbell Ritchie

Joined: Oct 13, 2005
Posts: 38040
To reverse a String: easy.
  • Use its toCharArray() method to get it into an array.
  • Write a [public static void] swapPair(char[] arr, int i, int j) method.
  • Write a [public static void] reverseArray(char[] arr) method which iterates along � the array and repeatedly swaps pairs ef elements. Be careful about the numbering of the elements. to avoid ArrayIndexOutOfBoundsExceptions.
  • Pass the resulting char[] array to the constructor of the String class.
  • I am sure there are other ways to do it.

    It would have been a lot easier if you had been told to use 32-character Strings, since int numbers use 32 bits.

    I hope that has given you something to get on with. Good luck with the exercise.
    Rob Spoor

    Joined: Oct 27, 2005
    Posts: 19655

    new StringBuilder(myString).reverse().toString();

    Although this does create a new object.

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