@CallerSensitive
public Class<?> getCallerClass ()

Gets the Class object of the caller who invoked the method that invoked getCallerClass.

This method filters reflection, java.lang.invoke.MethodHandle, and hidden frames regardless of the SHOW_REFLECT_FRAMES and SHOW_HIDDEN_FRAMES options this StackWalker has been configured with.

This method should be called when a caller frame is present. If it is called from the bottom most frame on the stack, IllegalCallerException will be thrown.

This method throws UnsupportedOperationException if this StackWalker is not configured with the RETAIN_CLASS_REFERENCE option.

Returns:  Class object of the caller's caller invoking this method.

Exceptions:

UnsupportedOperationException		if this StackWalker is not configured with Option.RETAIN_CLASS_REFERENCE.
IllegalCallerException		if there is no caller frame, i.e. when this getCallerClass method is called from a method which is the last frame on the stack.

@apiNote For example, Util::getResourceBundle loads a resource bundle on behalf of the caller. It invokes getCallerClass to identify the class whose method called Util::getResourceBundle. Then, it obtains the class loader of that class, and uses the class loader to load the resource bundle. The caller class in this example is MyTool.

 class Util {
     private final StackWalker walker = StackWalker.getInstance(Option.RETAIN_CLASS_REFERENCE);
     public ResourceBundle getResourceBundle(String bundleName) {
         Class<?> caller = walker.getCallerClass();
         return ResourceBundle.getBundle(bundleName, Locale.getDefault(), caller.getClassLoader());
     
 }

 class MyTool {
     private final Util util = new Util();
     private void init() {
         ResourceBundle rb = util.getResourceBundle("mybundle");
     }
 }
 }

An equivalent way to find the caller class using the walk method is as follows (filtering the reflection frames, MethodHandle and hidden frames not shown below):

     Optional<Class<?>> caller = walker.walk(s ->
         s.map(StackFrame::getDeclaringClass)
          .skip(2)
          .findFirst());
 

When the getCallerClass method is called from a method that is the bottom most frame on the stack, for example, static public void main method launched by the java launcher, or a method invoked from a JNI attached thread, IllegalCallerException is thrown.