如何检查作为Class对象的参数的instanceof？ [英] How to check instanceof on an argument that is a Class object?

问题描述

我试图建立一个通用类加载器。我需要检查我加载的方法参数的类，以确定它们是否是同一个类。

I'm trying to build a generic class loader. I need to check classes that I load against a method argument to determine if they are of the same class.

代码主要解释我想要做什么。

The code mostly explains what I'm trying to do.

private static LinkedList<Object> loadObjectsInDirectory(Class class0, File dir) throws ClassNotFoundException {

            LinkedList<Feature> objects = new LinkedList<Object>();

            ClassLoader cl = new GenericClassLoader();

            for(String s : dir.list()) {
                Class class1 = cl.loadClass(s);
                try {
                    Object x = class1.newInstance();
                    if (x instanceof (!!! class0 !!!) ) {
                        objects.add(x);
                    }
                } catch (InstantiationException ex) {
                } catch (IllegalAccessException ex) {
                }

            }

            return objects;

        }

如何实现？

推荐答案

看起来您需要 isAssignableFrom 方法

if (kelass.isAssignableFrom(klass)) {
   objects.add(x);
}

JavaDoc

确定由此Class对象表示的类或接口是否与由指定的Class参数表示的类或接口相同，或者是超类或超接口。如果是这样，返回true;否则返回false。如果这个Class对象表示一个原始类型，如果指定的Class参数正是这个Class对象，那么此方法返回true;

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class object represents a primitive type, this method returns true if the specified Class parameter is exactly this Class object; otherwise it returns false.

具体来说，此方法测试由指定的Class参数表示的类型是否可以通过身份转换转换为由此Class对象表示的类型，通过扩展参考转换。有关详细信息，请参阅Java语言规范第5.1.1和5.1.4节。

Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion or via a widening reference conversion. See The Java Language Specification, sections 5.1.1 and 5.1.4 , for details.

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