Java 8 BiPredicate示例

「爱情、让人受尽委屈。」 2023-02-15 05:11 8阅读 0赞

在Java 8中， [BiPredicate][]是一个函数接口，它接受两个参数并返回一个布尔值，基本上，此`BiPredicate`与`Predicate`相同，相反，它需要2个参数进行测试。

@FunctionalInterface
    public interface BiPredicate<T, U> {
        boolean test(T t, U u);
    }

**进一步阅读**  
Java 8谓词示例

## 1. BiPredicate Hello World。 ##

如果字符串长度匹配提供的长度？

JavaBiPredicate1.java

package com.mkyong.java8;
    
    import java.util.function.BiPredicate;
    
    public class JavaBiPredicate1 {
    
        public static void main(String[] args) {
    
            BiPredicate<String, Integer> filter = (x, y) -> {
                return x.length() == y;
            };
    
            boolean result = filter.test("mkyong", 6);
            System.out.println(result);  // true
    
            boolean result2 = filter.test("java", 10);
            System.out.println(result2); // false
        }
    
    }

输出量

true
    false

## 2. BiPredicate作为函数参数。 ##

本示例使用`BiPredicate`通过域名或威胁分数过滤不良域名。

JavaBiPredicate2.java

package com.mkyong.java8;
    
    import java.util.Arrays;
    import java.util.List;
    import java.util.function.BiPredicate;
    import java.util.stream.Collectors;
    
    public class JavaBiPredicate2 {
    
        public static void main(String[] args) {
    
            List<Domain> domains = Arrays.asList(new Domain("google.com", 1),
                    new Domain("i-am-spammer.com", 10),
                    new Domain("mkyong.com", 0),
                    new Domain("microsoft.com", 2));
    
            BiPredicate<String, Integer> bi = (domain, score) -> {
                return (domain.equalsIgnoreCase("google.com") || score == 0);
            };
    
            // if google or score == 0
            List<Domain> result = filterBadDomain(domains, bi);
            System.out.println(result); // google.com, mkyong.com
    
            //  if score == 0
            List<Domain> result2 = filterBadDomain(domains, (domain, score) -> score == 0);
            System.out.println(result2); // mkyong.com, microsoft.com
    
            // if start with i or score > 5
            List<Domain> result3 = filterBadDomain(domains, (domain, score) -> domain.startsWith("i") && score > 5);
            System.out.println(result3); // i-am-spammer.com
    
            // chaining with or
            List<Domain> result4 = filterBadDomain(domains, bi.or(
                    (domain, x) -> domain.equalsIgnoreCase("microsoft.com"))
            );
            System.out.println(result4); // google.com, mkyong.com, microsoft.com
    
    
        }
    
        public static <T extends Domain> List<T> filterBadDomain(
                List<T> list, BiPredicate<String, Integer> biPredicate) {
    
            return list.stream()
                    .filter(x -> biPredicate.test(x.getName(), x.getScore()))
                    .collect(Collectors.toList());
    
        }
    }
    
    class Domain {
    
        String name;
        Integer score;
    
        public Domain(String name, Integer score) {
            this.name = name;
            this.score = score;
        }
        // getters , setters , toString
    }

输出量

[Domain{name='google.com', score=1}, Domain{name='mkyong.com', score=0}]
    [Domain{name='mkyong.com', score=0}]
    [Domain{name='i-am-spammer.com', score=10}]
    [Domain{name='google.com', score=1}, Domain{name='mkyong.com', score=0}, Domain{name='microsoft.com', score=2}]

## 参考文献 ##

*  [BiPredicate JavaDoc][BiPredicate]
 *  [Java 8方法参考：如何使用它][Java 8]
 *  Java 8谓词示例

标签： [过滤器][Link 1] [功能接口][Link 2] [高阶功能][Link 3] [Java 8][Java 8 1] [谓词][Link 4]

> 翻译自: [https://mkyong.com/java8/java-8-bipredicate-examples/][https_mkyong.com_java8_java-8-bipredicate-examples]

[BiPredicate]: https://docs.oracle.com/javase/8/docs/api/java/util/function/BiPredicate.html
[Java 8]: https://www.codementor.io/@eh3rrera/using-java-8-method-reference-du10866vx
[Link 1]: https://mkyong.com/tag/filter/
[Link 2]: https://mkyong.com/tag/functional-interface/
[Link 3]: https://mkyong.com/tag/higher-order-function/
[Java 8 1]: https://mkyong.com/tag/java-8/
[Link 4]: https://mkyong.com/tag/predicate/
[https_mkyong.com_java8_java-8-bipredicate-examples]: https://mkyong.com/java8/java-8-bipredicate-examples/