Formatting Binary Output

Question

I want to format binary output in text fields to confrom to the following scheme:
head data1 data2 return offSet id
6 bits 5 bits 5 bits 5 bits 5 bits 6 bits
where the first row are field names and the second is the filed width.
What that means is that, using the value 1 (base 10) as an example, a 6 bit filed will read 000001 and so a 5 bit field will read 00001.
My program converts to binary no worries, but how do I enforce the width requirements? I am using Integer.toBinaryString(int) to convert, if that helps.
Thanks

Answer 1

public String intToJustifiedBinaryString(int number, int length)
  StringBuffer buffer = new StringBuffer(Integer.toBinaryString(number));
  while (buffer.length() < length)
      buffer.insert(0, "0");
  return buffer.toString();It works great! Now for the learning. I looked up StringBuffer and found this explanation:
StringBuffer(String str)
Constructs a string buffer so that it represents the same sequence of characters as the string argument; in other words, the initial contents of the string buffer is a copy of the argument string.
What I am trying to figure out is how it is not overwriting what already exists in the buffer. Lets pretend with int = 7 and a 6 bit field.
So initially, buffer.length() = 3 and my buffer looks like 1 1 1.
From the API: The principal operations on a StringBuffer are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string buffer. The append method always adds these characters at the end of the buffer; the insert method adds the characters at a specified point.
If I am specifying my insert point as 0 (insert(int offset, char c) Inserts the string representation of the char argument into this string buffer.) How am I not overwriting one of my bits comprising my binary 7? My only guess is that insert operation first shifts what is already there over the necessary amount, based on the length of what is being inserted, before inserting at the specified point. I have read nothing to support this theory. Please let me know if it is correct.
Thanks for the help!