从 Java 8 forEach 循环返回一个值
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Return a value from Java 8 forEach loop
提问by Punter Vicky
In the below example , someObjects is a set. I am trying to return true if a condition matches within the loop , however this doesn't seem to compile. However when I just add "return" it works fine.What is the issue that I need to fix?
在下面的例子中， someObjects 是一个集合。如果循环中的条件匹配，我试图返回 true ，但这似乎无法编译。但是，当我添加“return”时它工作正常。我需要解决什么问题？
public boolean find(){
someObjects.forEach(obj -> {
if (some_condition_met) {
return true;
}
});
return false;
}
Compilation Errors
编译错误
The method forEach(Consumer) in the type Iterable is not applicable for the arguments (( obj) -> {})
Iterable 类型中的 forEach(Consumer) 方法不适用于参数 (( obj) -> {})
采纳答案by pablochan
The forEachmethod in a Collectionexpects a Consumerwhich means a function that takes a value, but doesn't return anything. That's why you can't use return true;but a return;works fine.
a 中的forEach方法Collection需要 a Consumer，这意味着函数接受一个值，但不返回任何内容。这就是为什么你不能使用return true;但 areturn;工作正常的原因。
I you want to break out of the loop when your condition is met, it's better to use a simple for(...)loop. I assumed that the type of objis Object:
我想在满足条件时跳出循环，最好使用简单的for(...)循环。我假设的类型obj是Object：
for (Object obj : someObjects) {
if (some_condition_met) {
return true;
}
}
return false;
回答by Ousmane D.
forEachaccepts a Consumertherefore you cannot pass in a behaviour that does not return void. you need to do something like:
forEach接受 aConsumer因此您不能传递不返回void的行为。您需要执行以下操作：
return someObjects.stream().anyMatch(e -> condition);
回答by Jason Hu
I guess you want to do this:
我猜你想这样做：
public boolean find(){
return someObjects.stream().anyMatch(o -> your_condition);
}
