#8: Streams are thread safe

Here's the writeInt() method from java.io.DataOutputStream:

public final void writeInt(int v) throws IOException {
  OutputStream out = this.out;
  out.write((v >>> 24) & 0xFF);
  out.write((v >>> 16) & 0xFF);
  out.write((v >>>  8) & 0xFF);
  out.write((v >>>  0) & 0xFF);
  written += 4;
}

Solution:

1. Never use the same stream in more than one thread

2. Don't chain multiple filters in parallel to one underlying stream (series is OK)