Java，枚举 : (short) - someNumber

Question

我正在寻找 Apache Storm 的源代码，我遇到了一些我从未见过的东西:CLOSE_MESSAGE((short)-100) 或 CLOSE_MESSAGE((short)-100 ).为什么要从 short 类型中减去 someNumber？这是什么意思？这是实际代码:

enum ControlMessage {
  CLOSE_MESSAGE((short)-100),
  EOB_MESSAGE((short)-201),
  OK_RESPONSE((short)-200),
  FAILURE_RESPONSE((short)-400),
  SASL_TOKEN_MESSAGE_REQUEST((short)-202),
  SASL_COMPLETE_REQUEST((short)-203);

private short code;

//private constructor
private ControlMessage(short code) {
    this.code = code;
}

/**
 * Return a control message per an encoded status code
 * @param encoded
 * @return
 */
static ControlMessage mkMessage(short encoded) {
    for(ControlMessage cm: ControlMessage.values()) {
      if(encoded == cm.code) return cm;
    }
    return null;
}

int encodeLength() {
    return 2; //short
}

/**
 * encode the current Control Message into a channel buffer
 * @throws Exception
 */
ChannelBuffer buffer() throws IOException {
    ChannelBufferOutputStream bout = new ChannelBufferOutputStream(ChannelBuffers.directBuffer(encodeLength()));      
    write(bout);
    bout.close();
    return bout.buffer();
}

void write(ChannelBufferOutputStream bout) throws IOException {
    bout.writeShort(code);        
} 
}

Answer 1

不，我不认为它在减去数字。它正在转换 int 为short!枚举有一个接受 short 作为参数的构造函数，所以它只是意味着将负整数传递给构造函数!