用JDK 8(1.8.0_212(编译代码,但无法使用JDK 11(11.0.3(校正Oracle JDK和Open JDK(AWS Corretto(
尝试使用Javac和Maven(Maven版本3.6.1和Maven-Compiler-Plugin版本3.8.0(编辑它的JDK 8,而JDK 11。
。import java.net.URL;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.function.Function;
import java.util.stream.Stream;
public class AppDemo {
public static void main(String[] args) {
// NO error here
giveMeStream("http://foo.com").map(wrap(url -> new URL(url)));
List<String> list = new ArrayList<String>();
list.add("http://foo.com/, http://bar.com/");
// error: unreported exception MalformedURLException;
// must be caught or declared to be thrown
list.stream().flatMap(
urls -> Arrays.<String>stream(urls.split(",")).map(wrap(url -> new URL(url)))
);
// error: unreported exception MalformedURLException;
// must be caught or declared to be thrown
Stream.concat(
giveMeStream("http://foo.com").map(wrap(url -> new URL(url))),
giveMeStream("http://bar.com").map(wrap(url -> new URL(url))));
}
static Stream<String> giveMeStream(String s) {
return Arrays.stream(new String[]{s});
}
static <T, R, E extends Throwable> Function<T, R>
wrap(FunException<T, R, E> fn) {
return t -> {
try {
return fn.apply(t);
} catch (Throwable throwable) {
throw new RuntimeException(throwable);
}
};
}
interface FunException<T, R, E extends Throwable> {
R apply(T t) throws E;
}
}
错误:
Expected : No compilation error
Actual : compilation error for JDK11
Error message with JDK 11:
s.<String>stream(urls.split(",")).map(wrap(url -> new URL(url)))
^
AppDemo.java:24: error: unreported exception MalformedURLException; must be caught or declared to be thrown
giveMeStream("http://foo.com").map(wrap(url -> new URL(url))),
^
AppDemo.java:25: error: unreported exception MalformedURLException; must be caught or declared to be thrown
giveMeStream("http://bar.com").map(wrap(url -> new URL(url))));
^
3 errors
,因为可能对规格的略有更新是这样说的。有关系吗?它不会这样工作。
在此处将异常变成参数化类型没有真正的目的。另外,您将使用此代码制作RuntimeException
的链条。试试看:
static <T, R> Function<T, R> wrap(FunException<T, R> fn) {
return t -> {
try {
return fn.apply(t);
} catch (Error | RuntimeException ex) {
throw ex;
} catch (Throwable throwable) {
throw new RuntimeException("Checked exception in lambda", throwable);
}
};
}
interface FunException<T, R> {
R apply(T t) throws Throwable;
}
现在它将汇编罚款。
读者:不要这样做。处理Java规则(例如检查例外(的正确方法是处理它们。使用hacks来解决一种语言的本质,这仅意味着您的代码是非异常的(其他阅读您的代码的人都不会得到它,并且您将很难阅读他人的代码。这很糟糕(,倾向于与其他库的互动方式不好,并且应该有所帮助的各种功能(例如:在这里您会得到很多因果异常链,这些链使您的日志阅读和异常痕迹比所需的更加困难(。另外,这远处"脱离人迹罕至的路"会导致有趣的时期,例如用于编译不再编译的代码。