找到Java異常輸出時爲何常常有"$Proxy.."的緣由了

在代碼：java.lang.reflect.Proxy.getProxyClass(ClassLoader, Class<?>...) 中，能夠發現這一段代碼：

            String proxyPkg = null; // package to define proxy class in

   /*

    * Record the package of a non-public proxy interface so that the

    * proxy class will be defined in the same package.  Verify that

    * all non-public proxy interfaces are in the same package.

    */

   for (int i = 0; i < interfaces.length; i++) {

int flags = interfaces[i].getModifiers();

if (!Modifier.isPublic(flags)) {

   String name = interfaces[i].getName();

   int n = name.lastIndexOf('.');

   String pkg = ((n == -1) ? "" : name.substring(0, n + 1));

   if (proxyPkg == null) {

proxyPkg = pkg;

   } else if (!pkg.equals(proxyPkg)) {

throw new IllegalArgumentException(

   "non-public interfaces from different packages");

   }

}

   }

   if (proxyPkg == null) { // if no non-public proxy interfaces,

proxyPkg = ""; // use the unnamed package

   }

   {

/*

* Choose a name for the proxy class to generate.

*/

long num;

synchronized (nextUniqueNumberLock) {

   num = nextUniqueNumber++;

}

String proxyName = proxyPkg + proxyClassNamePrefix + num;

其中：

         private static long nextUniqueNumber = 0;

         private static Object nextUniqueNumberLock = new Object();

能夠發現，主要是nextUniqueNumberLock 這個字段是一直在增加的。因此纔會有"$Proxy7"、"java.lang.ClassCastException: $Proxy19"、"java.lang.NoSuchMethodException: $Proxy84"...等等的輸出了。