这与线程无关,仅与类加载器有关。相同的类定义,当被不同的类加载器加载时,被 JVM 视为两个不同的类。所以instanceof
或两者之间的转换失败。
所以回答你原来的问题:在同一个类加载器加载的线程之间传递对象是安全的,instanceof
等等。工作正常。
这是一篇关于类加载问题的文章。
另请参阅我的这个较早的答案,以了解验证游戏中存在哪些类加载器的方法。
更新罗曼的评论
以下是一些用于测试 的行为的代码instanceof
,其中包括:
URL[] urls = new URL[] {new File("build/classes/").toURL()};
ClassLoader loader1 = new URLClassLoader(urls, null);
ClassLoader loader2 = new URLClassLoader(urls, null);
Class<?> c1 = loader1.loadClass("net.torokpeter.Foo");
Class<?> c2 = loader2.loadClass("net.torokpeter.Foo");
Object foo1 = c1.newInstance();
Object foo2 = c2.newInstance();
System.out.println("c1.toString(): " + c1);
System.out.println("c2.toString(): " + c2);
System.out.println("c1.equals(c2): " + c1.equals(c2));
System.out.println("c1 == c2: " + (c1 == c2));
System.out.println("foo1: " + foo1);
System.out.println("foo2: " + foo2);
System.out.println("foo1 instanceof Foo: " + (foo1 instanceof Foo));
System.out.println("foo2 instanceof Foo: " + (foo2 instanceof Foo));
System.out.println("c1.isAssignableFrom(c1): " + c1.isAssignableFrom(c1));
System.out.println("c2.isAssignableFrom(c2): " + c2.isAssignableFrom(c2));
System.out.println("c1.isAssignableFrom(c2): " + c1.isAssignableFrom(c2));
System.out.println("c2.isAssignableFrom(c1): " + c2.isAssignableFrom(c1));
System.out.println("c1.isAssignableFrom(Foo.class): " + c1.isAssignableFrom(Foo.class));
System.out.println("c2.isAssignableFrom(Foo.class): " + c2.isAssignableFrom(Foo.class));
System.out.println("Foo.class.isAssignableFrom(c1): " + Foo.class.isAssignableFrom(c1));
System.out.println("Foo.class.isAssignableFrom(c2): " + Foo.class.isAssignableFrom(c2));
输出是(在 Eclipse,Java5 中):
c1.toString(): class net.torokpeter.Foo
c2.toString(): class net.torokpeter.Foo
c1.equals(c2): false
c1 == c2: false
foo1: net.torokpeter.Foo@360be0
foo2: net.torokpeter.Foo@45a877
foo1 instanceof Foo: false
foo2 instanceof Foo: false
c1.isAssignableFrom(c1): true
c2.isAssignableFrom(c2): true
c1.isAssignableFrom(c2): false
c2.isAssignableFrom(c1): false
c1.isAssignableFrom(Foo.class): false
c2.isAssignableFrom(Foo.class): false
Foo.class.isAssignableFrom(c1): false
Foo.class.isAssignableFrom(c2): false
所以一切似乎都是一致的:-)