java - JML 中带返回的 If 语句

Question

我需要设置一个后置条件，确保在 size_ 为 0 时返回 null。基于

 if(size_ == 0)
  return null;

我怎样才能在 jml 中做到这一点？有任何想法吗？以下不起作用:

//@ ensures size_ == null ==> \return true;

提前致谢

Answer 1

尝试

//@ ensures size_ == null ==> \result == true;

例子:

//@ ensures size_ == null ==> \result == true;
public boolean sizeUndefined() {
    if (size_ == null)
        return true;

    return size_.length() > 0;
}

你也可以简单地这样写:

//@ ensures size_ == null ==> \result;

这里是 the documentation for \result :

3.2.14 \result
Within a normal postcondition or a modification target of a non-void method, the special identifier \result is a specification expression whose type is the return type of the method. It denotes the value returned by the method. \result is allowed only within an ensures, also_ensures, modifies, or also_modifies pragma that modifies the declaration of a non-void method.