反射:Class、Method

最新推荐文章于 2024-01-24 08:41:34 发布

最新推荐文章于 2024-01-24 08:41:34 发布 · 139 阅读

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#java

本文深入解析 Java 中的 Class 类，介绍其如何表示运行时的类和接口，包括枚举、注释、数组类型及原始类型等。文章还探讨了如何通过 Class 对象获取类型名称，并介绍了 Method 类提供的方法信息。

java.lang .Class

Instances of the class Class represent classes and interfaces in a running Java application. An enum is a kind of class and an annotation(注释) is a kind of interface. Every array also belongs(属于) to a class that is reflected as aClass object that is shared(共享) by all arrays with the same element type and number of dimensions. The primitive（原生） Java types (boolean,byte, char, short, int, long, float, and double), and the keyword void are also represented as Class objects.

Class has no public constructor. Instead Class objects are constructed automatically(自动) by the Java Virtual Machine as classes are loaded and by calls to thedefineClass method in the class loader.

The following example uses a Class object to print the class name of an object:

     void printClassName(Object obj) {
         System.out.println("The class of " + obj +
                            " is " + obj.getClass().getName());
     }

It is also possible to get the Class object for a named type (or for void) using a class literal (JLS Section15.8.2). For example:

     System.out.println("The name of class Foo is: "+Foo.class.getName());

java.lang.reflect .Class Method

A Method provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method).

A Method permits（允许） widening (扩展)conversions to occur when matching(匹配) the actual(实际) parameters to invoke with the underlying(底层) method's formal parameters, but it throws anIllegalArgumentException if a narrowing (收缩)conversion would occur.