Raw use of parameterized class 'List'
时间: 2024-09-10 07:19:43 浏览: 16
"Raw use of parameterized class 'List'" 是Java编程语言中使用泛型时可能出现的一个警告或错误信息。在Java 5之前,Java集合框架(如List、Set等)没有使用泛型,这意味着它们可以存储任意类型的对象。自从引入泛型之后,开发者可以指定集合应该持有的对象类型,从而提供了更好的类型安全性,同时减少了类型转换的需要。
当开发者在代码中使用没有明确指定泛型类型参数的集合类时,就会出现"Raw use of parameterized class 'List'"的警告或错误。简而言之,这是指你使用了带有类型参数的集合类(如`List`),但没有指定它应该存储的对象类型。
例如,以下代码将会触发这种警告:
```java
List list = new ArrayList(); // 使用了未指定类型的List
```
而正确的使用方式应该是:
```java
List<String> list = new ArrayList<String>(); // 指定了List中元素的类型为String
```
或者更现代的钻石操作符(Java 7及以上):
```java
List<String> list = new ArrayList<>(); // 省略了右侧的类型参数,编译器可以推断类型
```
相关问题
Raw use of parameterized class
The raw use of a parameterized class refers to using the class without specifying the type parameter. In languages like Java or C#, parameterized classes allow you to create classes that can work with different types. However, if you use the class without specifying the type parameter, it is considered a raw use.
For example, let's say we have a generic class called `Box` that can hold any type of object:
```java
public class Box<T> {
private T value;
public void setValue(T value) {
this.value = value;
}
public T getValue() {
return value;
}
}
```
If we use this class without specifying the type parameter, it becomes a raw use:
```java
Box box = new Box(); // Raw use of Box
box.setValue("Hello"); // No type safety
String value = (String) box.getValue(); // Type casting required
```
In the above example, `Box box = new Box();` is a raw use because we are not specifying the type parameter. This results in the loss of type safety, as we can assign any type of value to the `value` field without any compiler checks. We also need to perform explicit type casting when retrieving the value.
It is generally recommended to avoid raw uses of parameterized classes as they bypass the type safety provided by generics and can lead to runtime errors or unexpected behavior.
Raw use of parameterized class 'ResponseDTO'
The "Raw use of parameterized class 'ResponseDTO'" error typically occurs when a generic class or interface is being used without specifying the type argument. In Java, parameterized classes allow you to define classes that can work with different data types.
To resolve this error, you need to specify the type argument when using the generic class or interface. For example, if you have a class called `ResponseDTO` that takes a type parameter, you need to provide the actual type when creating an instance of that class.
Here's an example of how you can fix the error by specifying the type argument for the `ResponseDTO` class:
```java
ResponseDTO<String> response = new ResponseDTO<>();
```
In this example, the type argument `<String>` specifies that the `ResponseDTO` class will work with `String` objects.
By providing the type argument, you ensure that the generic class is used correctly and avoid the "Raw use of parameterized class" error.