groovy.transform

Annotation Type EqualsAndHashCode

@Documented
@Retention(value=RUNTIME)
@Target(value=TYPE)
public @interface EqualsAndHashCode

Class annotation used to assist in creating appropriate equals() and hashCode() methods.

It allows you to write classes in this shortened form:

 import groovy.transform.EqualsAndHashCode
 @EqualsAndHashCode
 class Person {
     String first, last
     int age
 }
 def p1 = new Person(first:'John', last:'Smith', age:21)
 def p2 = new Person(first:'John', last:'Smith', age:21)
 assert p1 == p2
 def map = [:]
 map[p1] = 45
 assert map[p2] == 45
 

The @EqualsAndHashCode annotation instructs the compiler to execute an AST transformation which adds the necessary equals and hashCode methods to the class.

The hashCode() method is calculated using Groovy's HashCodeHelper class which implements an algorithm similar to the outlined in the book Effective Java.

The equals() method compares the values of the individual properties of the class.

Since:

1.8.0

Author:

Paul King

See Also:

HashCodeHelper

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
boolean	callSuper Whether to include super in equals and hashCode calculations
String	excludes Comma separated list of field and property names to exclude from equals and hashCode calculations
boolean	includeFields Include fields as well as properties in equals and hashCode calculations

Element Detail

excludes

public abstract String excludes

Comma separated list of field and property names to exclude from equals and hashCode calculations

Default:

""

callSuper

public abstract boolean callSuper

Whether to include super in equals and hashCode calculations

Default:

false

includeFields

public abstract boolean includeFields

Include fields as well as properties in equals and hashCode calculations

Default:

false