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.favtuts.java8;

import java.util.function.BiPredicate;

public class JavaBiPredicate {
    
    public static void main(String[] args) {
        BiPredicate<String, Integer> filter = (x, y) -> {
            return x.length() == y;
        };

        boolean result = filter.test("favtuts", 7);
        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.favtuts.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("tuts.heomi.net", 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, tuts.heomi.net

        //  if score == 0
        List<Domain> result2 = filterBadDomain(domains, (domain, score) -> score == 0);
        System.out.println(result2); // tuts.heomi.net, 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, tuts.heomi.net, 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
    @Override
    public String toString() {
        return "Domain{" +
            " name='" + getName() + "'" +
            ", score='" + getScore() + "'" +
            "}";
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getScore() {
        return this.score;
    }

    public void setScore(Integer score) {
        this.score = score;
    }
}

Output

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

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/java8

References

• BiPredicate JavaDoc
• Java 8 Method Reference: How to Use it
• Java 8 Predicate Examples