Question

我有一组类对象，它们在变量handlers中扩展这个抽象类：

public abstract class RequestHandler {

    public boolean handleGet(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handlePost(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handlePut(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handleDelete(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handleTrace(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handleOptions(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handleConnect(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }

    public boolean handlePatch(final HttpServletRequest request, final HttpServletResponse response) {
        return true;
    }
}

我现在想把这个集合映射到BiFunction的列表：

    final List<BiFunction<HttpServletRequest, HttpServletResponse, Boolean>> getHandlers = Arrays.stream(handlers)
            .<BiFunction<HttpServletRequest, HttpServletResponse, Boolean>>map(handler -> handler::handleGet)
            .collect(Collectors.toList());

如果我删除显式泛型类型规范：

    final List<BiFunction<HttpServletRequest, HttpServletResponse, Boolean>> getHandlers = Arrays.stream(handlers)
            .map(handler -> handler::handleGet)
            .collect(Collectors.toList());

我在handler::handleGet收到了编译错误：

对象不是功能界面

为什么编译器没有正确推断出这里的类型？谢谢！

Java 8：将对象映射到方法引用时，类型推断失败

0 个答案: