https://openjdk.java.net/ 
public interface javax.swing.event.TreeWillExpandListener extends java.util.EventListener
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: javax.swing.event.TreeWillExpandListener
  super_class: java.lang.Object
{
  public abstract void treeWillExpand(javax.swing.event.TreeExpansionEvent);
    descriptor: (Ljavax/swing/event/TreeExpansionEvent;)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Exceptions:
      throws javax.swing.tree.ExpandVetoException
    MethodParameters:
       Name  Flags
      event  

  public abstract void treeWillCollapse(javax.swing.event.TreeExpansionEvent);
    descriptor: (Ljavax/swing/event/TreeExpansionEvent;)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Exceptions:
      throws javax.swing.tree.ExpandVetoException
    MethodParameters:
       Name  Flags
      event  
}
SourceFile: "TreeWillExpandListener.java"