Java : ClassNotFoundException with Examples
ClassNotFoundException (Java SE 21 & JDK 21) with Examples.
You will find code examples on most ClassNotFoundException methods.
Summary
Thrown when an application tries to load in a class through its string name using: The forName method in class Class. The findSystemClass method in class ClassLoader . The loadClass method in class ClassLoader.
public class Foo {
}
public class Main {
public static void main(String[] args) {
try {
// A Foo class exists.
final var foo = Class.forName("Foo");
System.out.println("foo : " + foo);
// A Bar class does not exist.
final var bar = Class.forName("Bar");
} catch (ClassNotFoundException e) {
System.out.println("ClassNotFoundException! : " + e.getMessage());
}
}
}
// Result
// ↓
//> java Main
//foo : class Foo
//ClassNotFoundException! : Bar
Constructors
ClassNotFoundException ()
Constructs a ClassNotFoundException with no detail message.
final var e = new ClassNotFoundException();
System.out.println(e); // java.lang.ClassNotFoundException
ClassNotFoundException (String s)
Constructs a ClassNotFoundException with the specified detail message.
final var e = new ClassNotFoundException("abcde");
System.out.println(e); // java.lang.ClassNotFoundException: abcde
System.out.println(e.getMessage()); // abcde
ClassNotFoundException (String s, Throwable ex)
Constructs a ClassNotFoundException with the specified detail message and optional exception that was raised while loading the class.
final var ex = new ClassNotFoundException("XYZ");
final var e = new ClassNotFoundException("abc", ex);
System.out.println(e); // java.lang.ClassNotFoundException: abc
System.out.println(e.getMessage()); // abc
System.out.println(e.getException()); // java.lang.ClassNotFoundException: XYZ
System.out.println(e.getException().getMessage()); // XYZ
Methods
Throwable getException ()
Returns the exception that was raised if an error occurred while attempting to load the class.
final var ex = new ClassNotFoundException("XYZ");
final var e = new ClassNotFoundException("abc", ex);
System.out.println(e); // java.lang.ClassNotFoundException: abc
System.out.println(e.getMessage()); // abc
System.out.println(e.getException()); // java.lang.ClassNotFoundException: XYZ
System.out.println(e.getException().getMessage()); // XYZ
Methods declared in Throwable
addSuppressed, fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, getSuppressed, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString
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