Question

当前在Groovy中，我需要编写以下代码来实现简单的逻辑：

def sampleList = [1, 2]
def element = sampleList.find { it == 3 }
if (!element) {
    throw new IllegalStateException('Element not found!')
}

使用Java Streams只是简单一点：

def sampleList = [1, 2]
sampleList.stream().filter { it == 3 }.findFirst().orElseThrow {
    new IllegalStateException('Element not found!')
}

是否有其他简洁的Groovy语法来执行相同的任务？

Answer 1

选项1 我认为这是最清晰的方法，利用Optional API：

def sampleList = [1, 2]
def element = Optional.ofNullable(sampleList.find{it==3}).orElseThrow{new IllegalStateException('Element not found!')}

选项2

我认为这不是很好，但是您可以从闭包中调用throw，并使用elvis ?:运算符

def sampleList = [1, 2]
def element = sampleList.find{it==3} ?: {throw new IllegalStateException('Element not found!')}()
//Alternately: ...{throw new IllegalStateException('Element not found!')}.call() to make it more readable

抛出：

Exception thrown

java.lang.IllegalStateException: Element not found!
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at ConsoleScript20$_run_closure2.doCall(ConsoleScript20:2)
    at ConsoleScript20$_run_closure2.doCall(ConsoleScript20)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at ConsoleScript20.run(ConsoleScript20:2)
    at jdk.internal.reflect.GeneratedMethodAccessor218.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

在Groovy控制台中

选项3 另一个选择是将所有逻辑提取到命名闭包中：

def sampleList = [1, 2]
def tester = {list, value -> if(value in list){value} else{throw new IllegalStateException('Element not found!')}}

tester(sampleList, 3)

Groovy是否具有用于收集中的find元素的专用语法，或者如果找不到则抛出异常？

1 个答案: