Med Java

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====== Send parameters to a thread and retrieve results from it in Java threads ======

To send parameters to a thread and retrieve results from it in Java, you typically use the **Callable** interface and **Future** objects. 

The **Callable** interface is similar to Runnable, but it can return a value and throw exceptions. 

A **Future** object represents the result of an asynchronous computation and can be used to retrieve the Callable's return value once the computation has completed.

<code java WordLengthCallable.java>
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutionException;

// A class that implements Callable
class WordLengthCallable implements Callable<Integer> {
    private final String word;

    public WordLengthCallable(String word) {
        this.word = word;
    }

    @Override
    public Integer call() {
        // Returning the length of the word
        return word.length();
    }
}

public class CallableExample {
    public static void main(String[] args) {
        // Creating a thread pool with one thread
        ExecutorService executor = Executors.newSingleThreadExecutor();

        // Creating a callable object
        WordLengthCallable callable = new WordLengthCallable("Hello, World");

        // Submitting the callable to the executor and getting a Future object
        Future<Integer> future = executor.submit(callable);

        try {
            // Getting the result from the Future object
            int length = future.get();
            System.out.println("Length of the word: " + length);
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        }

        // Shutting down the executor
        executor.shutdown();
    }
}
</code>

**Callable Implementation**: The WordLengthCallable class implements Callable<Integer> and overrides the call method. It takes a String parameter and returns the length of the string.

**ExecutorService**: The ExecutorService is used to manage and execute Callable tasks. In this example, a single-threaded executor is created.

**Submitting Callable**: The callable object is submitted to the executor using the submit method, which returns a Future object. This Future object represents the result of the Callable.

**Retrieving Result**: The future.get() method is used to retrieve the result of the Callable. This method blocks until the computation is complete.

**Handling Exceptions**: The code handles InterruptedException and ExecutionException, which can be thrown while waiting for the result.

**Shutting Down Executor**: Finally, the executor is shut down to prevent the program from running indefinitely.

This example demonstrates a clean way to pass parameters to a thread and retrieve results from it in Java. 

Using **Callable** and **Future** makes it easier to manage threads and process their results, especially when dealing with tasks that return values or might throw exceptions.