How Java implements asynchronous programming using Guava
Guava is an open source Java library released by Google, providing many practical tool classes and methods. This includes support for concurrent programming, making asynchronous programming simpler and more efficient. Guava's asynchronous programming module provides a callback based approach to handling asynchronous tasks to avoid blocking the main thread and improve system performance.
Guava's asynchronous programming module includes the following commonly used key methods:
1. ListenableFuture: Provides a more user-friendly interface for handling the results of asynchronous tasks. Compared to the Future interface provided by JDK, it supports registering callback functions to process results without actively blocking the retrieval of results.
The following is an example code for using ListenableFuture:
import com.google.common.util.concurrent.*;
ListenableFuture<String> future = Executors.newSingleThreadExecutor().submit(() -> "Hello World");
Futures.addCallback(future, new FutureCallback<String>() {
@Override
public void onSuccess(String result) {
System.out.println(result);
}
@Override
public void onFailure(Throwable t) {
System.out.println("Error: " + t.getMessage());
}
});
2. ListenableFutureTask: is a class that inherits from FutureTask and extends the functionality of some asynchronous operations. It provides an addListener() method that can trigger a callback function after the task is completed.
The following is an example code for using ListenableFutureTask:
import com.google.common.util.concurrent.*;
ListenableFutureTask<String> futureTask = ListenableFutureTask.create(() -> "Hello World");
futureTask.addListener(() -> {
try {
System.out.println(futureTask.get());
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}, MoreExecutors.directExecutor());
ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.submit(futureTask);
3. Futures: Provides some tools and methods for handling asynchronous tasks. The most commonly used methods are allAsList() and successfulAsList(), which return the results of all tasks in a ListenableFuture object list and only successful task results, respectively.
The following is an example code for using Futures:
import com.google.common.util.concurrent.*;
List<ListenableFuture<String>> futures = new ArrayList<>();
futures.add(Executors.newSingleThreadExecutor().submit(() -> "Hello"));
futures.add(Executors.newSingleThreadExecutor().submit(() -> "World"));
ListenableFuture<List<String>> allFutures = Futures.allAsList(futures);
Futures.addCallback(allFutures, new FutureCallback<List<String>>() {
@Override
public void onSuccess(List<String> result) {
System.out.println(result);
}
@Override
public void onFailure(Throwable t) {
System.out.println("Error: " + t.getMessage());
}
});
To use Guava's asynchronous programming module, you need to add the following dependencies to the pom.xml file of the project:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>30.1-jre</version>
</dependency>
This way, you can import com. Google. common. util. concurrent. *; Let's import Guava's asynchronous programming related classes.
