引发异常的 Java 8 Lambda 函数? [英] Java 8 Lambda function that throws exception?

问题描述

我知道如何创建对具有 String 参数并返回 int 的方法的引用，它是:

I know how to create a reference to a method that has a String parameter and returns an int, it's:

Function<String, Integer>

但是，如果函数抛出异常，这将不起作用，比如它被定义为:

However, this doesn't work if the function throws an exception, say it's defined as:

Integer myMethod(String s) throws IOException

我将如何定义此引用?

推荐答案

您需要执行以下操作之一.

You'll need to do one of the following.

• 如果是您的代码，则定义您自己的功能接口来声明已检查的异常:

• If it's your code, then define your own functional interface that declares the checked exception:

@FunctionalInterface
public interface CheckedFunction<T, R> {
   R apply(T t) throws IOException;
}

并使用它:

void foo (CheckedFunction f) { ... }

否则，将 Integer myMethod(String s) 包装在未声明已检查异常的方法中:

Otherwise, wrap Integer myMethod(String s) in a method that doesn't declare a checked exception:

public Integer myWrappedMethod(String s) {
    try {
        return myMethod(s);
    }
    catch(IOException e) {
        throw new UncheckedIOException(e);
    }
}

然后:

Function<String, Integer> f = (String t) -> myWrappedMethod(t);

或:

Function<String, Integer> f =
    (String t) -> {
        try {
           return myMethod(t);
        }
        catch(IOException e) {
            throw new UncheckedIOException(e);
        }
    };

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