1 package com.github.javaparser.ast; 2 3 /** 4 * A key to a piece of user data associated with a {@link Node} at runtime. 5 * The key contains type information that can be used to check the 6 * type of any user data value for the key when the value is set. UserDataKey is abstract in order to 7 * force the creation of a subtype. That subtype is used to test for identity when looking for the 8 * user data because actual object identity would suffer from problems under serialization. 9 * So, the correct way to declare a UserDataKey is like this: 10 * 11 * <pre> 12 * <code> 13 * public static final UserDataKey<Role> ROLE = new UserDataKey<Role>() { }; 14 * </code> 15 * </pre> 16 * 17 * This code was taken from the <a href="http://wicket.apache.org/">Wicket project</a>. 18 * 19 * @param <T> 20 * The type of the object which is stored 21 * 22 * @see Node#getUserData(UserDataKey) 23 */ 24 public abstract class UserDataKey<T> { 25 @Override 26 public int hashCode() 27 { 28 return getClass().hashCode(); 29 } 30 31 /** 32 * @see java.lang.Object#equals(java.lang.Object) 33 */ 34 @Override 35 public boolean equals(Object obj) 36 { 37 return obj != null && getClass().equals(obj.getClass()); 38 } 39 } 40
