Java Predicate or()

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In this guide, you will learn about the Predicate or() method in Java programming and how to use it with an example.

1. Predicate or() Method Overview

Definition:

The Predicate.or() is a default method available in the Predicate interface. It is used to combine two predicates using a logical OR operation. The resultant predicate evaluates to true if either the original or the specified predicate evaluates to true.

Syntax:

default Predicate<T> or(Predicate<? super T> other)

Parameters:

- other: A predicate which will be logically OR-ed with the current predicate.

Key Points:

- The or() method allows the combination of multiple predicate conditions with an OR operation.

- It is useful when a data set needs to be filtered based on one of several conditions.

- If either the current predicate or the specified predicate evaluates to true, the composite predicate will also evaluate to true.

2. Predicate or() Method Example

import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;

public class PredicateOrExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "Anna", "Aria");

        // Define a Predicate to test if a name starts with the letter 'A'
        Predicate<String> startsWithA = name -> name.startsWith("A");
        // Define a Predicate to test if a name length is exactly 3
        Predicate<String> lengthIs3 = name -> name.length() == 3;

        // Combine the two predicates using or()
        Predicate<String> combinedPredicate = startsWithA.or(lengthIs3);

        for (String name : names) {
            if (combinedPredicate.test(name)) {
                System.out.println(name);
            }
        }
    }
}

Output:

Alice
Bob
Anna
Aria

Explanation:

In the provided example, we first define two separate predicates - one to check if a name starts with the letter 'A' and another to check if the length of the name is exactly 3. 

Using the or() method, these two predicates are combined to form a composite predicate. As a result, the names "Alice", "Bob", "Anna", and "Aria" from the list are printed, as they satisfy at least one of the conditions.