Applications and best practices of Java generics in collections

Answer the question: The application of Java generics on collections, including providing type-safe collections, reducing NullPointerExceptions, and enhancing readability and maintainability. Specific application: Force specific type elements to improve type safety. Prevent null values ​​and reduce exceptions. Use meaningful type parameters to improve code readability. Avoid over-generics and keep your code simple. Consider using wildcards for greater flexibility. Avoid primitive types, use wrapper classes. Follow naming conventions and use single-letter type parameter names.

Application and best practices of Java generics in collections

Generics allow you to specify the elements when creating a collection types, thereby improving type safety and reducing errors. The following are common applications of generics in Java:

Type-safe collections

Generic collections force elements of a specific type to be added to the collection, thus preventing type mismatches and abnormal. For example:

List<String> names = new ArrayList<>();
names.add("John"); // 正确
names.add(10); // 错误，类型不匹配

Reduce NullPointerExceptions

Generic collections will not accept null elements unless explicitly stated. This helps reduce the occurrence of NullPointerExceptions. For example:

List<Customer> customers = new ArrayList<>();
customers.add(new Customer("John", "Doe")); // 正确
customers.add(null); // 错误，不允许 null 值

Enhance code readability and maintainability

Using generics can make the code easier to read and maintain. It explicitly specifies the type of elements in the collection, eliminating the need for type guessing. For example:

List<Integer> numbers = new ArrayList<>();
// 操作数字
for (int number : numbers) {
    // ...
}

Best practices:

• Use meaningful type parameters: Choose ones that clearly represent the types of elements in the collection Type parameters.
• Don’t over-genericize: Use generics only for collections that require them.
• Consider using wildcards: When dealing with collections of unknown types, you can use the wildcard character (?) for a more flexible solution.
• Avoid primitive types: For primitive types, use their wrapper class (such as Integer).
• Follow naming conventions: The convention is to use single-letter names for type parameters, such as T or E.

Practical case:

Consider a sample project where we have a collection that stores customer objects:

class Customer {
    private String firstName;
    private String lastName;
    // ...
}

// 使用泛型创建客户集合
List<Customer> customers = new ArrayList<>();

// 添加客户对象
customers.add(new Customer("John", "Doe"));
customers.add(new Customer("Jane", "Smith"));

// 迭代集合，打印客户姓名
for (Customer customer : customers) {
    System.out.println(customer.getFirstName() + " " + customer.getLastName());
}

By using generics , we ensure that there are only Customer objects in the collection, preventing type mismatches and errors.

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