What are the costs of creating Java objects?

There is overhead in Java object creation, including memory allocation, constructor calls, and class loading. The exact cost depends on the heap size, class size, and code execution time. In practice, it takes about 1000 milliseconds to create 1 million integer objects. Optimization strategies include using object pools, thread-local storage, and lazy initialization.

Overhead of Java object creation

Creating objects in Java will incur certain overhead, including:

• Memory allocation: New objects require memory allocation from the heap. Allocating memory takes time, depending on the size of the heap and current memory usage.
• Constructor call: Each object has a constructor, which is called when the object is created. The constructor executes initialization code, which takes time.
• Class loading: If the class of the object to be created has not been loaded, you need to load the class. The class loading process can be time-consuming, especially for large classes.

Practical case: Creating 1 million integer objects

To demonstrate the object creation overhead, let us create an array containing 1 million integer objects:

// 导入必要的类
import java.util.Arrays;

// 创建一个包含 100 万个整数的数组
int[] arr = new int[1000000];

// 测量创建数组所需的时间
long startTime = System.currentTimeMillis();
Arrays.fill(arr, 1);
long endTime = System.currentTimeMillis();

// 打印创建数组所需的时间
System.out.println("创建数组所需时间：" + (endTime - startTime) + " 毫秒");

Running this code, we can create an array of 1 million integers in about 1000 milliseconds. This time includes overhead such as memory allocation, constructor calls, and class loading.

Optimize object creation

In some cases, the object creation overhead can be optimized by:

• Object pooling : Store frequently used objects in the object pool instead of creating a new object for each request.
• Thread-local storage: Use thread-local storage in each thread to store thread-specific objects, thereby avoiding sharing objects across threads.
• Lazy initialization: Defer initializing certain properties of the object until they are needed.

The above is the detailed content of What are the costs of creating Java objects?. For more information, please follow other related articles on the PHP Chinese website!