在Lambda表达式中设置对象 [英] Set object in lambda expression

问题描述

如何将我的对象设置为lambda表达式中的另一个对象?我遇到错误

how could I set my object to another in lambda expression? I got error

lambda表达式中使用的

变量应为最终变量或有效最终变量

variable used in lambda expression should be final or effectively final

具有以下代码:

public MyObj myFun(MyObj o) {
   MyObj obj = null;

   myObjList.stream().filter(o -> ...).forEach(o -> {
      // I do some stuff here

      // I need here set obj to o, but I got error
      obj = o;
   });

   return myObj; // I need return found obj or null;
}

推荐答案

您不能将o分配给外部变量.但您可以将其作为流处理的结果返回.使用map代替forEach，然后从映射器返回o.然后执行findAny或findFirst-这将为您提供Optional<MyObj>.最后，执行orElse(null)返回找到并处理的对象；如果未找到，则返回null.

You can't assign o to the outer variable. But you can return it as a result of you stream processing. Use map instead of forEach and return o from the mapper. Then do findAny or findFirst - this will give you an Optional<MyObj>. Finally do orElse(null) to return the found and processed object or null if none was found.

MyObj obj = myObjList
   .stream()
   .filter(o -> ...)
   .map(o -> {
       // I do some stuff here

       // I need here set obj to o, but I got error
       return o;
   })
   .findAny()
   .orElse(null);

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