例如，我想创建一个注释 @Out 来定位参数。然后，我会以某种方式使用编译器来检查函数返回之前是否设置了参数值。这可行吗？
另外，我考虑了一个 @Immutable 注释，它不允许调用任何未注释为 @Const 的方法或访问任何公共字段（编译时和可能的运行时）。
到目前为止，我有这个：
另外，我考虑了一个 @Immutable 注释，它不允许调用任何未注释为 @Const 的方法或访问任何公共字段（编译时和可能的运行时）。
到目前为止，我有这个：
//I'm assuming Class retention is a subset of Runtime retention
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface Out
{
//no idea what to go in here.
}
这是另一个注释。同样，我没有完整的定义：
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Immutable
{
}
我认为我可以开始设计一种使用反射在运行时实现的策略，但我希望指示编译器或预处理器来检查那些内容，这样我的注释就不会有额外开销。
这是其中一件事情，你会想“如果这个能够被做到，它肯定已经存在了，如果它确实存在，那我该去哪里找它。”
编辑：经过进一步思考关于@Const和@Immutable，以及记住java通过值传递对象指针后，我扩展了@Const的定义，去掉了@Immutable，并修改了@Out的定义，如下所示：
/**
* When Applied to a method, ensures the method doesn't change in any
* way the state of the object used to invoke it, i.e., all the fields
* of the object must remain the same, and no field may be returned,
* unless the field itself is marked as {@code @Const}. A method
* annotated with {@code @Const} can only invoke other {@code @Const}
* methods of its class, can only use the class's fields to invoke
* {@code @Const} methods of the fields classes and can only pass fields
* as parameters to methods that annotate that formal parameter as
* {@code @Const}.
*
* When applied to a formal parameter, ensures the method will not
* modify the value referenced by the formal parameter. A formal
* parameter annotated as {@code @Const} will not be aliased inside the
* body of the method. The method is not allowed to invoke another
* method and pass the annotated parameter, save if the other method
* also annotates the formal parameter as {@code @Const}. The method is
* not allowed to use the parameter to invoke any of its type's methods,
* unless the method being invoked is also annotated as {@code @Const}
*
* When applied to a field, ensures the field cannot be aliased and that
* no code can alter the state of that field, either from inside the
* class that owns the field or from outside it. Any constructor in any
* derived class is allowed to set the value of the field and invoke any
* methods using it. As for methods, only those annotated as
* {@code @Const} may be invoked using the field. The field may only be
* passed as a parameter to a method if the method annotates the
* corresponding formal parameter as {@code @Const}
*
* When applied to a local variable, ensures neither the block where the
* variable is declared or any nested block will alter the value of that
* local variable. The local variable may be defined only once, at any
* point where it is in scope. Only methods annotated as
* {@code @Const} may be invoked using this variable, and the variable
* may only be passed as a parameter to another method if said method
* annotates its corresponding formal parameter as {@code @Const}
*
*/
@Retention(RetentionPolicy.SOURCE)
@Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD,
ElementType.LOCAL_VARIABLE})
@Inherited
public @interface Const
{
}
现在是@Out：
/**
* The formal parameter annotated with {@code @Out} must be undefined in
* the scope of the caller, and it's the responsibility of the method to
* define it. If allowNull is true, the parameter can be explicitly set
* to null in the body of the method.
*/
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.PARAMETER)
public @interface Out
{
boolean allowNull() default false;
}
编辑：我正在尝试将其实现为Eclipse插件，但是我完全不知道如何阅读手册。我编写了一个插件，其中包含访问AST和访问方法和字段的基本逻辑。然后我创建了一堆虚拟注释，我的插件应该检测到它们，然后我尝试打印结果，但我甚至不知道该期望什么。我的插件是“增量构建”插件。这是它的代码，如果有人可以看一下并向我解释一些东西，那就太好了。我在这个API中完全迷失了。
SOURCE。然后，您需要创建一个Processor，并在META-INF/services/javax.annotation.processing.Processor中定义您处理器实现的完全限定名称以将其附加到您的项目中。您还需要启用注解处理。缺点是您必须在错误/警告出现之前保存文件，而不是像内置的编译时检查一样立即出现。 - Dioxin@Const注释的内容即使从其他文件或依赖项中访问也将保持不可变。 - FinnTheHuman