java - @Nonnull 和 Objects.requireNonNull 有什么区别

Question

以下两个代码片段有什么区别。

public Integer getId(@Nonnull SomeObject obj){  
    // do some stuff
    return id;
}

public Integer getId(SomeObject obj){   
    Objects.requireNonNull(SomeObject, "SomeObject is null");
    // do some stuff
    return id;
}

它们之间的显着区别是什么。在这些情况下进行空检查的正确方法是什么。

Answer 1

两者是互补的:@Nonnull 注解记录了 obj 必须是非空的事实，而 Objects.requireNonNull 调用确保obj 在运行时是非空的。

你应该把两者结合起来，像这样:

public Integer getId(@Nonnull SomeObject obj){   
    Objects.requireNonNull(SomeObject, "SomeObject is null");
    // do some stuff
    return id;
}

关于@Nonnull的相关文档可以找到here :

Optional Type Annotations are not a substitute for runtime validation

Before Type Annotations, the primary location for describing things like nullability or ranges was in the javadoc. With Type annotations, this communication comes into the bytecode in a way for compile-time verification.

Your code should still perform runtime validation.