【一天一坑】空数组，使用 allMatch 默认返回true

大熊猫今天吃什么2025-04-22 21:45

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List<Integer> list = new ArrayList<>();
boolean flag = list.stream().allMatch(e -> e > 0);
//flag = true

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/**
 * Returns whether all elements of this stream match the provided predicate.
 * May not evaluate the predicate on all elements if not necessary for
 * determining the result.  If the stream is empty then {@code true} is
 * returned and the predicate is not evaluated.
 *
 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
 * terminal operation</a>.
 *
 * @apiNote
 * This method evaluates the <em>universal quantification</em> of the
 * predicate over the elements of the stream (for all x P(x)).  If the \* stream is empty, the quantification is said to be \<em\>vacuously \* satisfied\</em\> and is always {@code true} (regardless of P(x)).
 *
 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
 *                  <a href="package-summary.html#Statelessness">stateless</a>
 *                  predicate to apply to elements of this stream
 * @return {@code true} if either all elements of the stream match the
 * provided predicate or the stream is empty, otherwise {@code false}
 */