Java Stream allMatch()

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

1. Stream allMatch() Method Overview

Definition:

The Stream.allMatch() method is a terminal operation that returns a boolean indicating whether all elements of the stream match the given predicate. It's often used to determine if every element in the stream satisfies a particular condition.

Syntax:

boolean allMatch(Predicate<? super T> predicate)

Parameters:

- predicate: a non-interfering, stateless predicate to apply to elements of the stream.

Key Points:

- It's a terminal operation, which means it ends the pipeline and you cannot reuse the stream afterward.

- The method returns a boolean value.

- Like anyMatch(), it's a short-circuiting operation. It stops processing as soon as it finds an element that doesn't match the condition.

- If the stream is empty, then the result is true (considered vacuously true, because no elements failed to match the predicate).

- It processes elements in the order they appear until it finds a non-matching element or all elements have been processed.

2. Stream allMatch() Method Example

import java.util.stream.Stream;

public class StreamAllMatchExample {
    public static void main(String[] args) {
        Stream<String> fruitStream = Stream.of("apple", "banana", "cherry", "date", "elderberry");

        // Check if all fruit names have more than 4 characters
        boolean allFruitsHaveMoreThan4Chars = fruitStream.allMatch(fruit -> fruit.length() > 4);

        System.out.println("Do all fruit names have more than 4 characters? " + allFruitsHaveMoreThan4Chars);
    }
}

Output:

Do all fruit names have more than 4 characters? true

Explanation:

In the provided example: We have a stream of fruit names. Using allMatch(), we check if every fruit name has more than 4 characters. Since each name in the stream ("apple", "banana", "cherry", "date", "elderberry") has a length greater than 4, the result is true.