Java 8 BiPredicate Examples
In Java 8, BiPredicate is a functional interface, which accepts two arguments and returns a boolean, basically this BiPredicate
is same with the Predicate
, instead, it takes 2 arguments for the test.
@FunctionalInterface
public interface BiPredicate<T, U> {
boolean test(T t, U u);
}
Further Reading
Java 8 Predicate Examples
1. BiPredicate Hello World.
If the String length matches the provided length?
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
}
}
Output
true
false
2. BiPredicate as function argument.
This example uses BiPredicate
to filter bad domains by the domain name or threat score.
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
}
Output
[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}]
// if score == 0
List<Domain> result2 = filterBadDomain(domains, (domain, score) -> score == 0);
System.out.println(result2); // mkyong.com, microsoft.com
it result will show only // mkyong.com .. you should update the result
How can we use biPredicate for below snippet in the filter()
Map<Integer, String> result = hmap.entrySet().stream()
.filter(p->p.getKey().intValue() >22)
.filter(p -> p.getValue().startsWith(“K”))