Java Stream allMatch() Method

The allMatch() method in Java, part of the java.util.stream.Stream interface, is used to check if all elements of the stream match a given predicate. This method is useful when you need to verify that every element in a stream satisfies a specific condition.

Table of Contents

1. Introduction
2. allMatch() Method Syntax
3. Understanding allMatch()
4. Examples
   • Basic Usage
   • Using allMatch() with Complex Predicates
5. Real-World Use Case
6. Conclusion

Introduction

The allMatch() method is a terminal operation that returns true if all elements of the stream match the provided predicate, otherwise it returns false. This method is particularly useful for scenarios where you need to ensure that all elements in a stream meet a certain condition.

allMatch() Method Syntax

The syntax for the allMatch() method is as follows:

boolean allMatch(Predicate<? super T> predicate)

Parameters:

• predicate: A Predicate that represents the condition to be checked against the elements of the stream.

Returns:

• true if all elements match the predicate; otherwise, false.

Throws:

• This method does not throw any exceptions.

Understanding allMatch()

The allMatch() method processes each element of the stream and returns true if all elements match the given predicate. If any element does not match the predicate, it short-circuits and returns false.

Examples

Basic Usage

To demonstrate the basic usage of allMatch(), we will create a Stream and use allMatch() to check if all elements are positive.

Example

import java.util.stream.Stream;

public class AllMatchExample {
    public static void main(String[] args) {
        Stream<Integer> stream = Stream.of(1, 2, 3, 4, 5);

        // Use allMatch() to check if all elements are positive
        boolean allPositive = stream.allMatch(n -> n > 0);

        System.out.println("All elements are positive: " + allPositive);
    }
}

Output:

All elements are positive: true

Using allMatch() with Complex Predicates

This example shows how to use allMatch() with a more complex predicate to check if all elements are even.

Example

import java.util.stream.Stream;

public class AllMatchComplexExample {
    public static void main(String[] args) {
        Stream<Integer> stream = Stream.of(2, 4, 6, 8, 10);

        // Use allMatch() to check if all elements are even
        boolean allEven = stream.allMatch(n -> n % 2 == 0);

        System.out.println("All elements are even: " + allEven);
    }
}

Output:

All elements are even: true

Real-World Use Case

Validating User Input

In real-world applications, the allMatch() method can be used to validate user input, such as ensuring all inputs are within a certain range.

Example

import java.util.stream.Stream;

public class ValidateUserInputExample {
    public static void main(String[] args) {
        Stream<Integer> userInputs = Stream.of(25, 30, 35, 40, 45);

        // Use allMatch() to check if all inputs are within the range 20 to 50
        boolean validInputs = userInputs.allMatch(input -> input >= 20 && input <= 50);

        System.out.println("All user inputs are valid: " + validInputs);
    }
}

Output:

All user inputs are valid: true

Conclusion

The Stream.allMatch() method is used to check if all elements of the stream match a given predicate. This method is particularly useful for ensuring that all elements in a stream satisfy a specific condition. By understanding and using this method, you can efficiently manage and process streams of values in your Java applications, ensuring data integrity and meeting specific criteria.