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Why does the following code cause ClassNotFoundException?
public class App02 {
public static class A {
}
public static void main(String[] args) throws ClassNotFoundException {
try {
System.out.println("A.class.getCanonicalName() = " + A.class.getCanonicalName());
Class c = Class.forName("tests.App02.A"); //error on this line
System.out.println(c.getName());
}
catch(Exception e) {
e.printStackTrace();
}
}
}
Output:
A.class.getCanonicalName() = tests.App02.A
java.lang.ClassNotFoundException: tests.App02.A
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:190)
at tests.App02.main(App02.java:15)
267
ClassNotFoundException is a checked exception which occurs when an application tries to load a class through its fully-qualified name and can not find its definition on the classpath. This occurs mainly when trying to load classes using Class. forName(), ClassLoader. loadClass() or ClassLoader.
Creating an inner class is quite simple. You just need to write a class within a class. Unlike a class, an inner class can be private and once you declare an inner class private, it cannot be accessed from an object outside the class.
To instantiate an inner class, you must first instantiate the outer class. Then, create the inner object within the outer object with this syntax: OuterClass outerObject = new OuterClass(); OuterClass. InnerClass innerObject = outerObject.
Try Class c = Class.forName("tests.App02$A"). It's not a top-level class, so use $ to locate it.
188
You need to use $ to access the nested class:
Class c = Class.forName("tests.App02$A");
When you compile your class, you will notice that the nested class is named as: App02$A.class, under package tests. It would make more sense then.
27
Because you are using a canonical name, but you should use name (A.class.getName()).
In your case you should use Class c = Class.forName("tests.App02$A");
4
There is a helpful util in commons-lang which support these classes:
org.apache.commons.lang3.ClassUtils.get("tests.App02.A")
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