When working with collections in Java, it is often necessary to filter or manipulate the elements based on certain conditions. Traditionally, this involved writing loops and if statements. However, with the introduction of lambda expressions in Java 8, the process has become more concise and expressive.
Lambda expressions allow developers to write anonymous functions inline, making it easier to define filters and apply them to collections. Here’s a step-by-step guide on how to create filters using lambda expressions in Java.
Step 1: Define a collection
First, let’s define a collection of integers that we want to filter:
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
Step 2: Create a lambda expression
Next, we need to create a lambda expression that represents the condition we want to filter on. Lambda expressions have a simplified syntax:
(parameter list) -> { lambda body }
In our case, let’s create a lambda expression that filters out even numbers:
Predicate<Integer> isOdd = number -> number % 2 != 0;
Here, number -> number % 2 != 0 is the lambda expression that takes an integer as input (number) and checks if it is odd. The expression returns true if the number is odd, and false if it is even.
Step 3: Apply the filter
Now that we have our lambda expression, we can apply it to our collection using the filter() method from the Stream API:
List<Integer> oddNumbers = numbers.stream()
.filter(isOdd)
.collect(Collectors.toList());
Here, numbers.stream() converts our list into a stream, which allows us to apply various operations on the collection. The filter(isOdd) operation then applies our lambda expression as a filter, keeping only the odd numbers. Finally, the collect(Collectors.toList()) operation converts the filtered stream back into a list.
Step 4: Output the filtered elements
To see the filtered elements, we can simply iterate over the oddNumbers list and print them:
for (Integer number : oddNumbers) {
System.out.println(number);
}
Conclusion
Using lambda expressions, we can create concise and readable filters in Java. They allow us to express criteria for filtering in a more declarative way, reducing the amount of boilerplate code. Lambda expressions make it easy to work with collections, providing a powerful tool for filtering, sorting, and transforming data.
#References
#hashtags #Java #LambdaExpressions