What are the best practices for generic methods in Java?

Java generic method best practices include: providing explicit type parameters, preferring type wildcards, using primitive types sparingly, preferring boundary wildcards, and limiting type boundaries to necessary conditions. Practical case: The filter method is a practical application of a generic method, used to filter out even numbers.

Best Practices for Java Generic Methods

Generic methods can improve code reusability and code simplicity . Generic methods in Java should adhere to the following best practices:

1. Provide explicit type parameters

Generic methods should clearly specify their type parameters:

public static <T> List<T> filter(List<T> list, Predicate<T> predicate) {
    // ...
}

2. Prefer the use of type wildcards

When possible, using type wildcards instead of explicit type parameters can improve the flexibility of the code:

public static <T> boolean anyMatch(List<? extends T> list, Predicate<T> predicate) {
    // ...
}

3. Limit type bounds to necessary conditions

The type bounds of generic methods should only be limited to absolutely necessary conditions:

// 仅当需要对 T 实现 Comparable 接口时才使用此边界
public static <T extends Comparable<T>> T max(List<T> list) {
    // ...
}

4. Use primitive types with caution

Avoid using primitive types (such as List) if possible, as they break type safety:

// 使用泛型方法参数更安全
public static <T> List<T> concat(List<T> list1, List<T> list2) {
    // ...
}

5. Prefer boundary wildcards

Boundary wildcards (<?>) can be used to get and set elements without breaking type safety:

public static <T> void swap(List<T> list, int i, int j) {
    T temp = list.get(i);
    list.set(i, list.get(j));
    list.set(j, temp);
}

Practical case:

The filter method is a practical application example of a generic method:

public class FilterExample {

    public static void main(String[] args) {
        List<Integer> numbers = List.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        // 过滤出偶数
        List<Integer> evenNumbers = filter(numbers, n -> n % 2 == 0);
        System.out.println(evenNumbers); // [2, 4, 6, 8, 10]
    }

    private static <T> List<T> filter(List<T> list, Predicate<T> predicate) {
        List<T> filteredList = new ArrayList<>();
        for (T item : list) {
            if (predicate.test(item)) {
                filteredList.add(item);
            }
        }
        return filteredList;
    }
}

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