Android Studio中@override的含义 [英] The Meaning of @override in Android Studio

问题描述

我对 Android Studio 完全陌生，我想知道 Android Studio 中 @Override 语句的用途.

I am completely new to Android Studio and I want to know the purpose of the @Override statement in Android Studio.

推荐答案

@Override 是一个 Java 注释.它告诉编译器以下方法覆盖其超类.例如，假设您实现了一个 Person 类.

@Override is a Java annotation. It tells the compiler that the following method overrides a method of its superclass. For instance, say you implement a Person class.

public class Person {
   public final String firstName;
   public final String lastName;

   //some methods

   @Override public boolean equals(Object other) {
      ...
   }
}

person 类有一个 equals() 方法.equals 方法已经在 Person 的超类 Object<中定义/a>.因此，上面的equals() 实现是对Persons 的equals() 的重新定义.也就是说，Person 覆盖了 equals().

The person class has an equals() method. The equals method is already defined in Person's superclass Object. Therefore the above implementation of equals() is a redefinition of equals() for Persons. That is to say, Person overrides equals().

在没有明确注释的情况下覆盖方法是合法的.那么@Override 注释有什么用呢?如果您不小心尝试以这种方式覆盖 equals() 怎么办:

It is legal to override methods without explicitly annotating it. So what is the @Override annotation good for? What if you accidentally tried to override equals() that way:

public boolean equals(Person other) {
   ...
}

以上案例有一个bug.您打算覆盖 equals() 但您没有.为什么?因为真正的 equals() 获取一个 Object 作为参数，而你的 equals() 获取一个 Person 作为参数.编译器不会告诉您有关该错误的信息，因为编译器不知道您想要覆盖.就编译器而言，您实际上是想 重载 equals().但是，如果您尝试使用 @Override 注释覆盖 equals:

The above case has a bug. You meant to override equals() but you didn't. Why? because the real equals() gets an Object as a parameter and your equals() gets a Person as a parameter. The compiler is not going to tell you about the bug because the compiler doesn't know you wanted to override. As far as the compiler can tell, you actually meant to overload equals(). But if you tried to override equals using the @Override annotation:

@Override public boolean equals(Person other) {
   ...
}

现在编译器知道你有错误.你想覆盖但你没有.所以使用@Override 注解的原因是显式声明方法覆盖.

Now the compiler knows that you have an error. You wanted to override but you didn't. So the reason to use the @Override annotation is to explicitly declare method overriding.

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