CmdLineException：选项采用操作数

Question

在下面的代码中进行解析时，对于整数值，我看到错误。其余的String选项运行良好。有人可以指出int Options是否需要其他行为？

import org.kohsuke.args4j.*;

@Getter
@ToString
class foo {

 @Option(name = "--a",
          required = true)
  private String a;

 @Option(name = "--b",
          required = true)
  private String b;

 @Option(name = "--c",
          required = true)
  private String c;

 @Option(name = "--d",
          required = true)
  private int d;

public test(String[] args) throws RuntimeException {

    CmdLineParser parser = new CmdLineParser(this);
    try {
      parser.parseArgument(args);
    } catch (CmdLineException e) {
      throw new RuntimeException(e);
    }

  }

public static void main(String[] args) {
   String[] commandArgs = { "--a val1", 
                            "--b val2", 
                            "--c val3", 
                            "--d 12"    };
foo j = new foo(commandArgs);

}

}

错误：

Exception in thread "main" java.lang.RuntimeException: org.kohsuke.args4j.CmdLineException: Option "--d" takes an operand

我得到的错误仅适用于int选项。