我知道如何创建一个有String参数并返回int的方法的引用,它是:
Function<String, Integer>
然而,如果函数抛出异常,比如它被定义为:
Integer myMethod(String s) throws IOException
我该如何定义这个引用呢?
我知道如何创建一个有String参数并返回int的方法的引用,它是:
Function<String, Integer>
然而,如果函数抛出异常,比如它被定义为:
Integer myMethod(String s) throws IOException
我该如何定义这个引用呢?
当前回答
我在课堂上遇到了这个问题。forName和Class。newInstance在lambda中,所以我做了:
public Object uncheckedNewInstanceForName (String name) {
try {
return Class.forName(name).newInstance();
}
catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
throw new RuntimeException(e);
}
}
在lambda中,我没有调用Class.forName("myClass").newInstance(),而是调用uncheckedNewInstanceForName ("myClass")
其他回答
你可以使用ET。ET是一个用于异常转换/转换的小型Java 8库。
对于ET,它看起来是这样的:
// Do this once
ExceptionTranslator et = ET.newConfiguration().done();
...
// if your method returns something
Function<String, Integer> f = (t) -> et.withReturningTranslation(() -> myMethod(t));
// if your method returns nothing
Consumer<String> c = (t) -> et.withTranslation(() -> myMethod(t));
ExceptionTranslator实例是线程安全的,可以由多个组件共享。如果你喜欢,你可以配置更具体的异常转换规则(例如FooCheckedException -> BarRuntimeException)。 如果没有其他可用的规则,被检查的异常将自动转换为RuntimeException。
(声明:我是ET的作者)
我是一个小库的作者,它具有一些通用的魔法,可以在任何地方抛出任何Java异常,而不需要捕获它们,也不需要将它们包装到RuntimeException中。
用法: unchecked(() -> methodThrowingCheckedException())
public class UncheckedExceptions {
/**
* throws {@code exception} as unchecked exception, without wrapping exception.
*
* @return will never return anything, return type is set to {@code exception} only to be able to write <code>throw unchecked(exception)</code>
* @throws T {@code exception} as unchecked exception
*/
@SuppressWarnings("unchecked")
public static <T extends Throwable> T unchecked(Exception exception) throws T {
throw (T) exception;
}
@FunctionalInterface
public interface UncheckedFunction<R> {
R call() throws Exception;
}
/**
* Executes given function,
* catches and rethrows checked exceptions as unchecked exceptions, without wrapping exception.
*
* @return result of function
* @see #unchecked(Exception)
*/
public static <R> R unchecked(UncheckedFunction<R> function) {
try {
return function.call();
} catch (Exception e) {
throw unchecked(e);
}
}
@FunctionalInterface
public interface UncheckedMethod {
void call() throws Exception;
}
/**
* Executes given method,
* catches and rethrows checked exceptions as unchecked exceptions, without wrapping exception.
*
* @see #unchecked(Exception)
*/
public static void unchecked(UncheckedMethod method) {
try {
method.call();
} catch (Exception e) {
throw unchecked(e);
}
}
}
来源:https://github.com/qoomon/unchecked-exceptions-java
我会做一些一般的事情:
public interface Lambda {
@FunctionalInterface
public interface CheckedFunction<T> {
T get() throws Exception;
}
public static <T> T handle(CheckedFunction<T> supplier) {
try {
return supplier.get();
} catch (Exception exception) {
throw new RuntimeException(exception);
}
}
}
用法:
Lambda.handle(() -> method());
我使用一个名为unchecked()的重载实用程序函数来处理多个用例。
一些用法示例
unchecked(() -> new File("hello.txt").createNewFile());
boolean fileWasCreated = unchecked(() -> new File("hello.txt").createNewFile());
myFiles.forEach(unchecked(file -> new File(file.path).createNewFile()));
支持工具
public class UncheckedUtils {
@FunctionalInterface
public interface ThrowingConsumer<T> {
void accept(T t) throws Exception;
}
@FunctionalInterface
public interface ThrowingSupplier<T> {
T get() throws Exception;
}
@FunctionalInterface
public interface ThrowingRunnable {
void run() throws Exception;
}
public static <T> Consumer<T> unchecked(
ThrowingConsumer<T> throwingConsumer
) {
return i -> {
try {
throwingConsumer.accept(i);
} catch (Exception ex) {
throw new RuntimeException(ex);
}
};
}
public static <T> T unchecked(
ThrowingSupplier<T> throwingSupplier
) {
try {
return throwingSupplier.get();
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}
public static void unchecked(
ThrowingRunnable throwing
) {
try {
throwing.run();
} catch (Exception ex) {
throw new RuntimeException(ex);
}
}
}
我所做的是允许用户在异常情况下给出他实际想要的值。 我有一个像这样的东西
public static <T, R> Function<? super T, ? extends R> defaultIfThrows(FunctionThatThrows<? super T, ? extends R> delegate, R defaultValue) {
return x -> {
try {
return delegate.apply(x);
} catch (Throwable throwable) {
return defaultValue;
}
};
}
@FunctionalInterface
public interface FunctionThatThrows<T, R> {
R apply(T t) throws Throwable;
}
这个可以被称为:
defaultIfThrows(child -> child.getID(), null)