java - 为 API 在 CharSequence 和 String 之间进行选择

Question

这个问题在这里已经有了答案:

When to use CharSequence in an API (5 个回答)

关闭 5年前。

A String is-a CharSequence . Java 库中的许多方法都接受 CharSequence所以they operate more generally .有些类(class)有 String方法(例如 Writer.write(String) )并实现 Appendable具有等价的 CharSequence方法(例如，Writer.append(CharSequence))。

如果我正在编写一个委托(delegate)给这样一个类的类，并且需要一些文本输入，我可以选择该输入是 String或 CharSequence .通过为客户提供更多选择，选择后者使类(class)更加灵活。但我没有看到太多这样做的代码:文本参数几乎总是 String而不是 CharSequence .使用 CharSequence 是否有缺点？ ?是否有性能影响？或者仅仅是程序员的惯性或无知导致使用 String而不是 CharSequence ?

比较

class XMLWriter {
   private final Writer writer;

   // more stuff here

   public void writeComment(String text) {
      writer.write("<!-- ");
      writer.write(text);
      writer.write(" -->");
   }
}

与

class XMLWriter {
   private final Writer writer;

   // more stuff here

   public void writeComment(CharSequence text) {
      writer.write("<!-- ");
      writer.append(text);
      writer.write(" -->");
   }
}

Answer 1

引用 CharSequence Javadoc:

This interface does not refine the general contracts of the equals and hashCode methods. The result of testing two objects that implement CharSequence for equality is therefore, in general, undefined. Each object may be implemented by a different class, and there is no guarantee that each class will be capable of testing its instances for equality with those of the other. It is therefore inappropriate to use arbitrary CharSequence instances as elements in a set or as keys in a map.

因此 IMO 在使用 CharSequnce 作为 String 的替代品之前，我们必须三思而后行。