多个“匹配”检查一个流 [英] Multiple "match" checks in one stream

问题描述

是否可以检查数组（或集合）是否包含除5之外的元素5 和元素。在 one 流中返回布尔结果而不是使用两个流：

Is it possible to check if an array (or collection) contains element 5 and element other than 5. In one stream returning boolean result instead of using two streams:

int[] ints = new int[]{1, 2, 3, 4, 5};

boolean hasFive = IntStream.of(ints).anyMatch(num -> num == 5);
boolean hasNonFive = IntStream.of(ints).anyMatch(num -> num != 5);

boolean result = hasFive && hasNonFive;

推荐答案

在这种特殊情况下，即你想知道是否一个流或数组包含匹配和非匹配元素（一个匹配谓词否定的元素），你可以做得更简单。

In this specific case, i.e. you want to know whether a stream or array contains both, a matching and a nonmatching element (an element matching the predicate’s negation), you can do it much simpler.

首先，测试是否第一个元素匹配谓词或其否定，然后，搜索流是否包含相反的任何匹配：

First, test whether the first element matches the predicate or its negation, then, search whether the stream contains any match of the opposite:

IntPredicate predicate=i -> i==5;

if(ints.length>0 && predicate.test(ints[0]))
    predicate=predicate.negate();
boolean result = IntStream.of(ints).anyMatch(predicate);

就是这样。如果您没有数组或集合作为流源，而是任意流，则测试第一个元素有点棘手：

That’s it. In case you don’t have an array or collection as the stream source, but an arbitrary stream, testing the first element is a bit trickier:

IntPredicate[] tmp={ null };
Spliterator.OfInt sp=intStream.spliterator();
boolean result = sp.tryAdvance(
    (int i) -> tmp[0]=predicate.test(i)? predicate.negate(): predicate)
 && StreamSupport.intStream(sp, false).anyMatch(tmp[0]);

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