Intro Java Predicate Not Example

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Intro Java Predicate Not Example

這篇介紹Java Predicate Not Example。

Example

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In order to negate an existing predicate, the Predicate.not() static method added to Java 11.
The Predicate class is present in java.util.function package.

你可以使用
// invert a Predicate, will be even shorter with static import
collection.stream()
  .filter(Predicate.not(MyObject::isEmpty))
  .collect(Collectors.toList());

使用Predicate 來產生偶數、奇數集合的範例
List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
  
// creating a predicate for negation
Predicate<Integer> even = i -> i % 2 == 0;

// creating a predicate object which
// is negation os supplied predicate
Predicate<Integer> odd = Predicate.not(even);

// filtering the even number using even predicate
List<Integer> evenNumbers
	= list.stream().filter(even).collect(
		Collectors.toList());

// filtering the odd number using odd predicate
List<Integer> oddNumbers
	= list.stream().filter(odd).collect(
		Collectors.toList());