Application of JUC Latching and AQS Technology in Starting Architecture Design

What is JUC Latch?

JUC (java.util.concurrent) is an important toolkit in Java concurrent programming. CountDownLatch is a multi-thread synchronization tool used to wait for other threads to complete a task before continuing.

The role of JUC locking in Android application startup In the process of Android application startup, some initialization operations are usually required, such as loading resources, initializing databases, and preloading data. These operations may take a long time and affect the startup speed of the application. Using the JUC lock can wait for these operations to complete in the main thread before continuing to execute, thereby improving the startup speed and user experience of the application.

How to Optimize Android App Launch Using JUC Latching

• (1) Create a blocking object in the main thread, and set the initial value of the counter to the number of threads that need to wait.
• (2) In the thread that needs to wait, perform the corresponding initialization operation, and call the countDown() method of the blocking object after the operation is completed, and decrement the counter by 1.
• (3) Call the await() method of the locked object in the main thread, and wait for the counter to become 0, that is, all threads complete the initialization operation before continuing to execute.

What is AQS?

AQS (AbstractQueuedSynchronizer) is an abstract class in Java concurrent programming, which provides a framework for implementing synchronizers, such as locks and semaphores.

The role of AQS in Android application startup During the Android application startup process, some synchronous operations need to be performed, such as waiting for the network request to return, waiting for the completion of animation playback, and so on. These synchronous operations can be realized by using AQS to ensure that the main thread will not continue to execute until a certain condition is met, thereby avoiding data inconsistency or abnormal situations.

How to optimize Android app startup with AQS

• (1) Inherit the AQS class, implement its abstract methods, and define the conditions for synchronous operations.
• (2) Where synchronization is required, call the acquire() method of AQS and wait for the synchronization condition to be met.
• (3) After the synchronization condition is met, call the release() method of AQS to release the synchronization state and allow the main thread to continue execution.

Sample code analysis

We assume that during the application startup process, three time-consuming initialization operations need to be performed, namely loading resources, initializing the database, and preloading data. We want these operations to complete before continuing with the rest of the app's logic.

Application example of JUC latch:

public class MainActivity extends AppCompatActivity {
    private CountDownLatch latch;
​
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
​
        latch = new CountDownLatch(3);
​
        // 启动三个线程执行初始化操作        new Thread(new ResourceLoader()).start();
        new Thread(new DatabaseInitializer()).start();
        new Thread(new DataPreloader()).start();
​
        try {
            // 等待所有线程完成初始化操作            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
​
        // 所有初始化操作完成后，继续执行应用逻辑        // ...
    }
​
    private class ResourceLoader implements Runnable {
        @Override        public void run() {
            // 执行加载资源的初始化操作            // ...
​
            // 初始化操作完成后，调用countDown()方法            latch.countDown();
        }
    }
​
    private class DatabaseInitializer implements Runnable {
        @Override        public void run() {
            // 执行初始化数据库的操作            // ...
​
            // 初始化操作完成后，调用countDown()方法            latch.countDown();
        }
    }
​
    private class DataPreloader implements Runnable {
        @Override        public void run() {
            // 执行预加载数据的操作            // ...
​
            // 初始化操作完成后，调用countDown()方法            latch.countDown();
        }
    }
}

In the above code, we create a CountDownLatch object and set the initial value of the counter to 3, which means that we need to wait for three threads to complete the initialization operation. In the run() method of each thread, perform the corresponding initialization operation, and call the countDown() method of CountDownLatch after the operation is completed, and decrement the counter by 1. In the main thread, call the await() method of CountDownLatch to wait for the counter to become 0, that is, all threads complete the initialization operation before continuing to execute other logic of the application.

Application examples of AQS:

    private MySync sync;
​
    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
​
        sync = new MySync();
​
        // 启动一个线程执行耗时的初始化操作        new Thread(new Initializer()).start();
​
        try {
            // 等待满足同步条件            sync.acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
​
        // 同步条件满足后，继续执行应用逻辑
        // ...
    }
​
    private class MySync extends AbstractQueuedSynchronizer {
        @Override
        protected boolean tryAcquire(int arg) {
            // 定义同步条件，例如等待初始化操作完成            return isInitialized();
        }
​
        @Override        protected boolean tryRelease(int arg) {
            // 释放同步状态            setState(1);
            return true;
        }
​
        private boolean isInitialized()
​
{
      // 判断初始化操作是否完成，返回true表示已完成，可以继续执行应用逻辑
      // ...
    }
  }
​
private class Initializer implements Runnable {
    @Override public void run() {
      // 执行初始化操作 // ...
​
// 初始化操作完成后，调用release()方法释放同步状态 sync.release(0);
    }
  }
}
​
​

In the above code, we created a custom synchronizer class MySync, inherited AbstractQueuedSynchronizer, and implemented tryAcquire() and tryRelease() methods. In the tryAcquire() method, synchronization conditions are defined, such as waiting for initialization operations to complete. In the tryRelease() method, the synchronization state is released.

In the main thread, we create a MySync object and perform time-consuming initialization operations in a new thread. After the initialization operation is completed, call the release() method of the MySync object to release the synchronization state. In the main thread, call the acquire() method of the MySync object and wait for the synchronization condition to be satisfied, that is, the initialization operation is completed before continuing to execute other logic of the application.

The full text mainly analyzes the application of JUC locking and AQS technology in the startup architecture design. For more Android development technical issues, click the home page for details.

summary

JUC locking and AQS technology play an important role in the architecture design of Android application startup. JUC locking can solve the problem of synchronous execution of multi-thread initialization operations. By waiting for all threads to complete initialization operations before continuing to execute, the application startup speed and user experience are improved. The AQS technology can realize synchronous operation, ensuring that the main thread will not continue to execute until a certain condition is met, avoiding data inconsistency or abnormal situations.

In Android development, startup optimization is very important, because the user's first impression of the application is largely determined by the startup speed. By using JUC locking and AQS technology, the startup process of the application can be effectively optimized and the user experience can be improved.