What is the overhead of object wrapper classes in Java?

The overhead of object wrapper classes includes: memory overhead: additional allocation of space to store data values ​​and object references; performance overhead: object allocation and garbage collection; API compatibility: type conversion required. Optimization suggestions: avoid frequent conversions; use primitive types; use boxing/unboxing operations.

Overhead of object wrapper classes in Java

Object wrapper classes are used in Java to wrap basic data types into objects kind. During the development process, sometimes you need to convert between two different data types. In this case, you need to use an object wrapper class.

Overhead analysis

When using object wrapper classes, the following overhead will be generated:

• Memory overhead: Every Each object wrapper class instance allocates additional memory space to store basic data values ​​and references to objects.
• Performance overhead: Because object wrapper classes are objects, they will introduce additional overhead, such as object allocation, garbage collection, etc.
• API Compatibility: Object wrapper classes are not compatible with primitive types in Java, which means additional conversion operations are required when coding.

Optimization suggestions

In order to minimize the overhead of object wrapper classes, the following optimizations are recommended:

• Avoid Frequent conversions: Try to avoid frequent conversions between basic data types and object wrapper classes.
• Use primitive types: For basic data types that do not need to be converted to object wrapper classes, use primitive types directly.
• Use boxing/unboxing operations: If you need to convert between basic data types and object wrapper classes, use valueOf() and XxxValue () methods (such as Integer.valueOf() and intValue()) for boxing and unboxing operations.

Practical Case

Consider the following code example, which evaluates the performance difference between an object wrapper class and a primitive type:

long start = System.currentTimeMillis();
for (int i = 0; i < 10000000; i++) {
    int num = i;
}
long end = System.currentTimeMillis();
System.out.println("原始类型："+(end - start)+" 毫秒");

start = System.currentTimeMillis();
for (int i = 0; i < 10000000; i++) {
    Integer num = i;
}
end = System.currentTimeMillis();
System.out.println("对象包装类："+(end - start)+" 毫秒");

In In this example, the primitive type loop is much faster than the object wrapper class loop, which demonstrates the performance overhead of the object wrapper class.

The above is the detailed content of What is the overhead of object wrapper classes in Java?. For more information, please follow other related articles on the PHP Chinese website!