Reading a String backward

[G. Graz]

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 !

 
Public class Number{
 
private int integer; //value in decimal
private String binary;// two complement in value of string
static final int mask0 = 0 ; // Adds zeros to the positive numbers
static final int mask = 1 ; // Adds ones to the negative number
    static final int size = 16 ;  // Sets the legth to the 16 bit
 reprasentation
    static final int maskL = 0x7FFFFFFF ;
    int zero = 0;
 

public Number() // constructor set to zero
{
integer = 0;
}
 
public Number(int n) // integer constructor
{
integer = n;
binary = DTB(16,n);
 

}
 
public Number(String bin) //String constructor
{
binary = bin;
integer = BTD(bin);
 

}
 
public int get_integer() // accessor for integer
{
return integer;
}
 

public String get_binary()// accessor for binary
{
return binary;
}
 
private String DTB(int k, int n)// integer to bit "Two's Complement,
 K= String size, n = the number value
{
String result = "";
{
 
//result = Integer.toBinaryString(n); //I think I could also use this
 form the method of Integer wrapper class to produce the same result
 
while (n>0)
  {
 

    for (int i = 0 ; i < size ; i++ )
        {
  result = (n%2)+result;
  n= n/2;
 
    }
 
     return result ;
      }
 
    while (n<0)
      {
 
     for (int i = 0 ; i < size ; i++ )
     {
 
        result = (n & mask) + result ;
        n = n >>> 1 ;
      }
 
     return result ;
 
      }
 

 }
return result;
 
}
 
  private int BTD( String bin) // Returns the binary number back into
 the decimal value.
{
 
           int result = 0;
{
  for (int i=0; i<bin.length(); i++)
        {
  result = (result * 2) + (bin.charAt(i)-'0');
    }
 
 
             if(bin.charAt(0) == '1')
     {
   for (int i=0; i<bin.length(); i++)
    {

   if (bin.charAt(i) = 1)
     result = zero.insert(bin.charAt(i));
     else if (bin.charAt(i) != 0)
                   result = 1;
 
    }
 
}
 
   

[Campbell Ritchie]

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]

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

Although this does create a new object.