Strings and Regular Expressions - The Java Programming Language - page 493

13.4.2. Getting Data Out
To get a String object from a StringBuilder object, you simply invoke
the toString method. If you need a substring of the buffer, the substring
methods works analogously to those of String . If you want some or all
of the contents as a character array, you can use getChars , which is ana-
logous to String.getChars .
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBe-
gin)
Copies characters from this StringBuilder into the specified ar-
ray. The characters of the specified substring are copied in-
to the character array, starting at dst[dstBegin] . The specified
substring is the part of the string buffer from srcBegin up to
but not including srcEnd .
Here is a method that uses getChars to remove part of a buffer:
public static StringBuilder
remove(StringBuilder buf, int pos, int cnt) {
if (pos < 0 || cnt < 0 || pos + cnt > buf.length())
throw new IndexOutOfBoundsException();
int leftover = buf.length() - (pos + cnt);
if (leftover == 0) { // a simple truncation
buf.setLength(pos);
return buf;
}
char[] chrs = new char[leftover];
buf.getChars(pos + cnt, buf.length(), chrs, 0);
buf.setLength(pos);
buf.append(chrs);
return buf;
}