出于好奇,我查看了Optional
类方法,但对它的签名感到困惑。orElseThrow
我不明白为什么必须按原样声明它。orElseThrow
所以,我用原始方法的副本和我的简化变体做了一个实验:
public class Main<T> {
//This is original signature of Optional.orElseThrow method
public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X{
throw exceptionSupplier.get();
}
//This is my attempt to simplify it but it doesn't work without try-catch block
public T orElseThrow2(Supplier<Throwable> exceptionSupplier) throws Throwable{
throw exceptionSupplier.get();
}
public static void main(String[] args){
Main<Object> m = new Main<Object>();
m.orElseThrow(() -> new RuntimeException("ha")); //no warnings/errors shown
m.orElseThrow2(() -> new RuntimeException("sad")); //"Unhandled exception: java.lang.Throwable"
}
try-catch
为什么没有阻止我的方法不被接受?为什么在原始方法中扩展
Throwable
不需要try-catch
块,即使原始方法抛出一个Throwable
对象?