How to use

ensureOpen

method

in

java.io.BufferedWriter

/**
 * Flushes the output buffer to the underlying character stream, without
 * flushing the stream itself.  This method is non-private only so that it
 * may be invoked by PrintStream.
 */
void flushBuffer() throws IOException {
  synchronized (lock) {
    ensureOpen();
    if (nextChar == 0)
      return;
    out.write(cb, 0, nextChar);
    nextChar = 0;
  }
}

/**
 * Flushes the output buffer to the underlying character stream, without
 * flushing the stream itself.  This method is non-private only so that it
 * may be invoked by PrintStream.
 */
void flushBuffer() throws IOException {
  synchronized (lock) {
    ensureOpen();
    if (nextChar == 0)
      return;
    out.write(cb, 0, nextChar);
    nextChar = 0;
  }
}

/**
 * Writes a single character.
 *
 * @exception  IOException  If an I/O error occurs
 */
public void write(int c) throws IOException {
  synchronized (lock) {
    ensureOpen();
    if (nextChar >= nChars)
      flushBuffer();
    cb[nextChar++] = (char) c;
  }
}

/**
 * Writes a single character.
 *
 * @exception  IOException  If an I/O error occurs
 */
public void write(int c) throws IOException {
  synchronized (lock) {
    ensureOpen();
    if (nextChar >= nChars)
      flushBuffer();
    cb[nextChar++] = (char) c;
  }
}

/**
 * Writes a portion of a String.
 *
 * <p> If the value of the <tt>len</tt> parameter is negative then no
 * characters are written.  This is contrary to the specification of this
 * method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
 * superclass}, which requires that an {@link IndexOutOfBoundsException} be
 * thrown.
 *
 * @param  s     String to be written
 * @param  off   Offset from which to start reading characters
 * @param  len   Number of characters to be written
 *
 * @exception  IOException  If an I/O error occurs
 */
public void write(String s, int off, int len) throws IOException {
  synchronized (lock) {
    ensureOpen();
    int b = off, t = off + len;
    while (b < t) {
      int d = min(nChars - nextChar, t - b);
      s.getChars(b, b + d, cb, nextChar);
      b += d;
      nextChar += d;
      if (nextChar >= nChars)
        flushBuffer();
    }
  }
}

/**
 * Writes a portion of a String.
 *
 * <p> If the value of the <tt>len</tt> parameter is negative then no
 * characters are written.  This is contrary to the specification of this
 * method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
 * superclass}, which requires that an {@link IndexOutOfBoundsException} be
 * thrown.
 *
 * @param  s     String to be written
 * @param  off   Offset from which to start reading characters
 * @param  len   Number of characters to be written
 *
 * @exception  IOException  If an I/O error occurs
 */
public void write(String s, int off, int len) throws IOException {
  synchronized (lock) {
    ensureOpen();
    int b = off, t = off + len;
    while (b < t) {
      int d = min(nChars - nextChar, t - b);
      s.getChars(b, b + d, cb, nextChar);
      b += d;
      nextChar += d;
      if (nextChar >= nChars)
        flushBuffer();
    }
  }
}

ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
  ((off + len) > cbuf.length) || ((off + len) < 0)) {

ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
  ((off + len) > cbuf.length) || ((off + len) < 0)) {