Negative binary to decimal problem

[G. Graz]

I have an application that I am trying to convert a negative binary number to the negative decimal number. The method that I have below doing this is BTD. I can get the positive numbers to compute correctly but a negative binary number to negative decimal number I can not ? Any suggestions would be of great help !! Thank you!!

 
 
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 ;
 

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.length() == size && bin.charAt(0) == '1')
            result = (result & maskL) + result ;
    result = result >>> 1 ;
     }
 

return result;
}
 

 
}   

[Campbell Ritchie]

Difficult to see exactly what is going on.

Why are you using 16 for your length of String and a 32-bit representation? That is likely to confuse you.
The multiple return statements are bad form, and are also causing the while loops to terminate prematurely.
The names of the methods are confusing; it is not easy to read DTB and BTD.
In the BTD method you have an if, and you think the two statements after that will be executed if the condition is true. They won't. Because you have omitted the {} after the if, only one will be included in the if block and the statement with the unsigned right shift will execute regardless.

Suggest you implement a power method; I wrote a tongue-in-cheek power function in another language here; Ulf Dittmer correctly interpreted it in Java. Then you can add -power(2, 31) if you reach the end of the String, and iterate along the characters from 1 [for (int i = 1; i<bin.length(); i++)]

Suggest you don't call the class Number; there already is a java.lang.Number class and creating a class with the same name may cause severe confusion weeks later.