class must either be declared abstract or implement

当你在编程时遇到“class must either be declared abstract or implement”这样的提示，这通常出现在Java等支持面向对象编程的语言中。这意味着某个类声明了它会实现一个接口或是继承了一个抽象类，但却没有完整地实现所有必需的方法。 ### 具体解释 1. **Abstract Class 或 Interface** 如果一个类继承自另一个包含未实现方法的类（即抽象类），或者该类实现了某些接口，则需要对该抽象类的所有抽象方法或接口中的每个方法都提供具体的实现。如果不想这样做，这个类本身就需要被标记为`abstract`。 2. **解决方案** - **选择一**: 将当前类也设置成抽象类 (`abstract`) ，表示这是一个尚未完成全部功能定义的类，并允许其后代继续完善这些细节； ```java public abstract class MyClass implements SomeInterface { // 可以只部分实现SomeInterface里的方法 } ``` - **选择二**: 提供完整的具体方法实现。 ```java public class MyClass implements SomeInterface { @Override public void requiredMethod() { // 实现此方法的具体内容... } // 对于接口内其他方法同样如此处理... } ``` 3. **原因分析** 当创建非抽象类型的实例时，系统期望所有的操作都已经明确下来——换句话说就是每一个函数都应该有实际意义而非空壳状态；否则就会抛出上述错误信息提醒开发者去修正这一情况。 ### 示例说明假设存在如下的 `MyInterface.java` ```java public interface MyInterface { void doSomething(); } ``` 那么尝试构建如下未完全遵循规则的普通类将会失败： ```java // 错误示范 public class IncorrectClass implements MyInterface {} // 缺少doSomething的实际覆盖版本 ``` 而正确的做法可以是这两种之一： #### 方法A – 完整实现接口成员 ```java public class CorrectImplementation implements MyInterface { @Override public void doSomething(){ System.out.println("正在执行某件事情"); } } ``` #### 方法B – 声明自身为抽象形式 ```java public abstract class AbstractSolution implements MyInterface {} // 子类需负责落实剩余的任务定义 ```

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class must either be declared abstract or implement

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Class 'UsersServiceImpl' must either be declared abstract or implement abstract method 'queryUsersList()' in 'IUsersService'

Class 'ArticleServiceImpl' must either be declared abstract or implement abstract method 'findById(Integer)' in 'ArticleService'

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Class 'Anonymous class derived from OnClickListener' must either be declared abstract or implement abstract method 'onClick(View)' in 'OnClickListener'

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Class 'SearchService' must either be declared abstract or implement abstract method 'saveBatch(Collection<T>, int)' in 'IService'

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