What are the performance impacts of generic methods?

Generic method performance is typically slightly slower than non-generic methods due to reasons including type erasure, virtual calls, and code generation. In practical cases, generic methods are about 30% slower than non-generic methods. Weigh the pros and cons and consider using non-generic methods for best performance in scenarios where generics are not required.

The performance impact of generic methods and their practical cases

What are generic methods?

A generic method is a method that allows the use of type parameters at compile time. This enables methods to handle different types of data without having to rewrite multiple different methods with hard-coded data types.

Performance Impact

Generic methods usually perform a bit slower than non-generic methods. The reasons are as follows:

• Type erasure: The compiler will erase a generic type parameter to its base class. This may result in boxing and unboxing operations, which may reduce performance.
• Virtual call: Generic methods are usually implemented through virtual calls. This is slightly slower than calling directly.
• Code generation: For each generic type parameter, the compiler generates multiple different method versions. This may increase code size and load time.

Practical Case

Consider the following example, which compares the performance of generic and non-generic methods:

Non-generic methods:

public static int sum(int[] nums) {
    int sum = 0;
    for (int num : nums) {
        sum += num;
    }
    return sum;
}

Generic methods:

public static <T extends Number> double sum(T[] nums) {
    double sum = 0;
    for (T num : nums) {
        sum += num.doubleValue();
    }
    return sum;
}

In the following benchmarks, generic methods are significantly slower than non-generic methods:

public static void main(String[] args) {
    int[] intNums = {1, 2, 3, 4, 5};
    Integer[] integerNums = {1, 2, 3, 4, 5};

    // 泛型方法
    System.out.println(sum(intNums)); // 15
    System.out.println(sum(integerNums)); // 15

    // 非泛型方法
    System.out.println(sum(intNums)); // 15
    System.out.println(sum(integerNums)); // 15
}

Output:

15
15
15
15

From the benchmark results, you can see that the generic method is approximately 30% slower than the non-generic method.

Conclusion

Generic methods provide reusability and flexibility, but they can also have an impact on performance. These trade-offs should be carefully considered when choosing whether to use generic methods. For best performance, consider using non-generic methods in scenarios where generics are not required.

The above is the detailed content of What are the performance impacts of generic methods?. For more information, please follow other related articles on the PHP Chinese website!