选择列表的元素，直到Java 8 Lambdas满足条件 [英] Picking elements of a list until condition is met with Java 8 Lambdas

问题描述

我试图改变主意思考功能方式，并且最近面临一种情况，我需要从列表中获取元素，直到满足条件，我找不到一种简单的自然方式来实现这一点。显然我还在学习。

I am trying to switch my mind to think the functional way and recently faced a situation in which I needed to pick up elements from a list until a condition is met and I could not find an easy natural way of achieving this. Obviously I am still learning.

说我有这个清单：

List<String> tokens = Arrays.asList("pick me", "Pick me", "pick Me",
    "PICK ME", "pick me and STOP", "pick me", "pick me and Stop", "pick me");

// In a non lambdas was you would do it like below
List<String> myTokens = new ArrayList<>();
for (String token : tokens) {
    myTokens.add(token);
    if (token.toUpperCase().endsWith("STOP")) {
        break;
    }
}

提前感谢您的输入

注意：
在发布之前，我先阅读用谓词限制流但我无法看到我如何能够适应我的问题。任何帮助将不胜感激。

NOTE: Before publishing this I read Limit a stream by a predicate but I could not see how I can adapt that answer to my problem. Any help would be appreciated thanks.

推荐答案

一个选项使用一个收集器，它需要两个函数，一个用于向列表添加字符串，另一个用于组合以前可能并行创建的列表。对于每个，只有当前一个部分输出没有以一个以STOP结尾的元素结束时，它才会添加字符串或整个列表：

One option uses a collector requiring two functions one that adds strings to lists and another which combines lists previously potentially created in parallel. For each it adds the string or the whole list only if the previous partial output doesn't end with an element that that ends with STOP:

tokens.stream().collect(() -> new ArrayList<String>(), (l, e) -> {
    if(l.isEmpty() || !l.get(l.size()-1).toUpperCase().endsWith("STOP"))
        l.add(e);
}, (l1, l2) -> {
    if(l1.isEmpty() || !l1.get(l1.size()-1).toUpperCase().endsWith("STOP"))
        l1.addAll(l2);
});

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