Java 8 Consumer and Supplier Example

By Atul Rai | Last Updated: May 16, 2023 Previous       Next

Java 8 introduced several functional interfaces in the java.util.function package to support functional programming paradigms. Among these interfaces, Consumer and Supplier play vital roles by representing functions with specific input and output requirements.

In this article, we will explore the differences between Consumer and Supplier and provide examples to illustrate their usage.

1. Consumer

The Consumer<T> interface is designed to perform operations on objects without returning any result. It accepts a single input of type T and executes the desired action. The key method of the Consumer interface is accept(T t), which takes an argument of type T.

Let’s consider an example where we have a list of strings and we want to print each string on a separate line:

package org.websparrow;

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

public class ConsumerExample {
	
	public static void main(String[] args) {
		
		Consumer<String> printString = (str) -> System.out.println(str);

		List<String> stringList = Arrays.asList("India", "USA", "Thailand");
		
		stringList.forEach(printString);
	}
}

In the above example, we define a Consumer called printString, which takes a string as input and prints it to the console. We then create a list of strings and use the forEach method to apply the printString consumer to each element of the list.

Output:

India
USA
Thailand

Similar Post: Java 8 Predicate vs Function: A Comparison with Examples

2. Supplier

The Supplier<T> interface, on the other hand, represents a supplier of results of type T. It does not take any input and is responsible for generating or providing values when called. The primary method in the Supplier interface is get(), which returns a result of type T.

Let’s consider an example where we generate a random number using the Supplier interface:

package org.websparrow;

import java.security.SecureRandom;
import java.util.function.Supplier;

public class SupplierExample {

	public static void main(String[] args) {

		Supplier<Integer> randomNumber = () -> new SecureRandom().nextInt();
		Integer value = randomNumber.get();

		System.out.println("Random Number: " + value);
	}
}

In the above example, we define a Supplier called randomNumber, which generates a secure random number using the SecureRandom class. We then call the get() method on the randomNumber supplier to obtain the generated random number and print it to the console.

Output:

Random Number: 1461150494

Summary

The Consumer interface accepts an input of type T and performs some action on it, whereas the Supplier interface provides a result of type T without taking any input. Consumer is useful when you need to perform operations on objects or process a collection of elements, while Supplier is handy for generating or providing values on demand.

In Java 8, these functional interfaces, along with other interfaces in the java.util.function package, enable developers to write more concise and expressive code by leveraging functional programming concepts. Understanding the distinctions between Consumer and Supplier allows you to utilize them effectively in various scenarios, enhancing the flexibility and readability of your Java code.

References

1. Consumer- Java Doc
2. Supplier- Java Doc
3. Functional Interface – Java Doc