Java DoubleStream allMatch() Method

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

Table of Contents

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

Introduction

The allMatch() method returns true if all elements of the stream match the provided predicate. If any element does not match the predicate, the method returns false. This is a terminal operation and it short-circuits as soon as the answer is determined.

allMatch() Method Syntax

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

boolean allMatch(DoublePredicate predicate)

Parameters:

• predicate: A DoublePredicate 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 allows you to check if every element in a DoubleStream satisfies a given condition. If the stream is empty, it returns true, as there are no elements to violate the predicate.

Examples

Basic Usage

To demonstrate the basic usage of allMatch(), we will create a DoubleStream and check if all elements are greater than 0.

Example

import java.util.stream.DoubleStream;

public class AllMatchExample {
    public static void main(String[] args) {
        DoubleStream numbers = DoubleStream.of(1.1, 2.2, 3.3, 4.4, 5.5);

        // Check if all elements are greater than 0
        boolean allPositive = numbers.allMatch(n -> n > 0);

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

Output:

All elements are positive: true

Using allMatch() with Custom Predicate

This example shows how to use allMatch() with a custom predicate to check if all elements in a DoubleStream are even.

Example

import java.util.stream.DoubleStream;

public class CustomPredicateExample {
    public static void main(String[] args) {
        DoubleStream numbers = DoubleStream.of(2.0, 4.0, 6.0, 8.0, 10.0);

        // Check if all elements are even
        boolean allEven = numbers.allMatch(n -> n % 2 == 0);

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

Output:

All elements are even: true

Real-World Use Case

Verifying Temperatures within a Safe Range

In real-world applications, the allMatch() method can be used to verify if all temperature readings are within a safe range.

Example

import java.util.stream.DoubleStream;

public class TemperatureCheckExample {
    public static void main(String[] args) {
        DoubleStream temperatures = DoubleStream.of(36.5, 37.0, 36.8, 37.1, 36.9);

        // Check if all temperatures are within the safe range (36.5 to 37.5 degrees Celsius)
        boolean allSafe = temperatures.allMatch(temp -> temp >= 36.5 && temp <= 37.5);

        System.out.println("All temperatures are within the safe range: " + allSafe);
    }
}

Output:

All temperatures are within the safe range: true

Conclusion

The DoubleStream.allMatch() method is used to check if all elements of a stream match a given predicate. This method is particularly useful for verifying that all elements in a stream satisfy a specific condition. By understanding and using this method, you can efficiently perform validation checks on streams of double values in your Java applications.