Review

When a DataOutputStream instance wraps an underlying ByteArrayOutputStream instance,
it is recommended to flush or close the DataOutputStream before invoking the underlying instances's toByteArray(). Also, it is a good practice to call flush/close explicitly as mentioned for example here.

• missing/call

org/apache/commons/bcel6/generic/InstructionList.java

getByteCode()

class InstructionList {
    /**
     * When everything is finished, use this method to convert the instruction
     * list into an array of bytes.
     *
     * @return the byte code ready to be dumped
     */
    public byte[] getByteCode() {
        // Update position indices of instructions
        setPositions();
        ByteArrayOutputStream b = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream(b);
        try {
            for (InstructionHandle ih = start; ih != null; ih = ih.getNext()) {
                Instruction i = ih.getInstruction();
                i.dump(out); // Traverse list
            }
        } catch (IOException e) {
            System.err.println(e);
            return new byte[0];
        }
        return b.toByteArray();
    }

}

class FlushStreamBeforeGetBytes {
  byte[] pattern(Instruction i) {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    DataOutputStream dos = new DataOutputStream(baos);
    try {
      i.dump(dos);
      dos.flush();
    } catch (IOException e) {
      return new byte[0];
    }
    return baos.toByteArray();
  }
}