Oppiskele Lambdas in Real-World Applications | Best Practices and Real-World Applications

In modern Java development, lambda expressions are not just a syntactic convenience—they are a powerful tool for solving everyday programming challenges. You frequently encounter situations where concise, inline behavior is needed. Lambdas shine in data processing tasks, such as filtering and transforming collections, where they make code more readable and expressive. They are also invaluable for customizing configuration logic, implementing callback mechanisms, and streamlining event-driven programming. Whether you are loading configuration files, defining custom sorting rules, or handling asynchronous events, lambdas can reduce boilerplate and clarify intent.

Main.java


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package com.example;

import java.io.*;
import java.util.*;
import java.util.function.Function;

public class Main {
    public static <T> List<T> loadConfig(String filePath, Function<String, T> parser) throws IOException {
        List<T> result = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
            String line;
            while ((line = reader.readLine()) != null) {
                result.add(parser.apply(line));
            }
        }
        return result;
    }

    public static void main(String[] args) throws IOException {
        // Example config file: each line is "key=value"
        String tempFile = "config.txt";
        try (PrintWriter out = new PrintWriter(tempFile)) {
            out.println("host=localhost");
            out.println("port=8080");
        }

        List<Map.Entry<String, String>> entries = loadConfig(tempFile, line -> {
            String[] parts = line.split("=");
            return Map.entry(parts[0], parts[1]);
        });

        for (Map.Entry<String, String> entry : entries) {
            System.out.println(entry.getKey() + " -> " + entry.getValue());
        }

        new File(tempFile).delete();
    }
}

By allowing a lambda to define the parsing logic, the ConfigLoader example above demonstrates how lambdas can make your codebase more flexible and extensible. Instead of hardcoding a single parsing strategy, you let users inject their own logic, making the loader reusable for different formats. This approach encourages open/closed design: your classes are open for extension (via lambdas) but closed for modification. Lambdas also make it simple to implement plug-in behaviors, event handlers, and custom strategies without introducing unnecessary interfaces or subclasses.

Main.java


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package com.example;

public class Main {
    @FunctionalInterface
    interface TaskCompleteListener {
        void onComplete(String result);
    }

    public static void runTask(TaskCompleteListener listener) {
        // Simulate a task
        String result = "Task finished!";
        // Notify listener
        listener.onComplete(result);
    }

    public static void main(String[] args) {
        runTask(result -> System.out.println("Callback received: " + result));
    }
}

1. Which of the following is a common real-world application of lambda expressions in Java?

2. How do lambda expressions improve code flexibility in Java?

3. Suppose you are processing a list of user names and want to print only those that start with "A". How could a lambda help you achieve this?

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Osio 3. Luku 5

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Suggested prompts:

Can you give an example of using a lambda in a ConfigLoader?

What are some other real-world scenarios where lambdas improve Java code?

How do lambdas compare to anonymous inner classes in Java?

Pyyhkäise näyttääksesi valikon

Main.java


              123456789101112131415161718192021222324252627282930313233343536373839
            
package com.example;

import java.io.*;
import java.util.*;
import java.util.function.Function;

public class Main {
    public static <T> List<T> loadConfig(String filePath, Function<String, T> parser) throws IOException {
        List<T> result = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
            String line;
            while ((line = reader.readLine()) != null) {
                result.add(parser.apply(line));
            }
        }
        return result;
    }

    public static void main(String[] args) throws IOException {
        // Example config file: each line is "key=value"
        String tempFile = "config.txt";
        try (PrintWriter out = new PrintWriter(tempFile)) {
            out.println("host=localhost");
            out.println("port=8080");
        }

        List<Map.Entry<String, String>> entries = loadConfig(tempFile, line -> {
            String[] parts = line.split("=");
            return Map.entry(parts[0], parts[1]);
        });

        for (Map.Entry<String, String> entry : entries) {
            System.out.println(entry.getKey() + " -> " + entry.getValue());
        }

        new File(tempFile).delete();
    }
}

Main.java


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package com.example;

public class Main {
    @FunctionalInterface
    interface TaskCompleteListener {
        void onComplete(String result);
    }

    public static void runTask(TaskCompleteListener listener) {
        // Simulate a task
        String result = "Task finished!";
        // Notify listener
        listener.onComplete(result);
    }

    public static void main(String[] args) {
        runTask(result -> System.out.println("Callback received: " + result));
    }
}

1. Which of the following is a common real-world application of lambda expressions in Java?

2. How do lambda expressions improve code flexibility in Java?

3. Suppose you are processing a list of user names and want to print only those that start with "A". How could a lambda help you achieve this?

Oliko kaikki selvää?

Kiitos palautteestasi!

Osio 3. Luku 5