how to update Java constructors,equals,hash,etc. in eclipse?

Question

I wanted to know if anyone knows about a good way to update,constructors, equals,hash,to string, etc. generated by eclipse in Java. Lot's of time, after I use the auto-generated code-stubs, I add a member variable to the class, and then I need to delete the auto-generated code, and do it all over again. Is there a way to cause eclipse to add the new variable to the auto-generated code-stubs ?

edit: ok deleting is not essential, however I still have to go and generate each on of them, I'm looking for an automatic solution.

Answer 1

This isn't exactly a solution to your question, but I no longer use the Eclipse auto-generated methods, I use the Apache commons lang EqualsBuilder and HashCodeBuilder:

So, for instance you can do:

import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.apache.commons.lang3.builder.ReflectionToStringBuilder;

public class EqualsTest {
    private String foo;
    private int bar;

    // getters and setters

    @Override
    public String toString() {
        return ReflectionToStringBuilder.toString(this);
    }

    @Override
    public int hashCode() {
        return HashCodeBuilder.reflectionHashCode(this);
    }

    @Override
    public boolean equals(Object obj) {
        return EqualsBuilder.reflectionEquals(this, obj);
    }
}

This uses reflection, and doesn't need changing when you add a field. However, there are other options where you can specify the fields to use, and if you want to take into account the hashCode of the superclass as well.

EDIT: As has been pointed out, the reflection aspect of this may have some performance penalties associated. Personally, I don't use the reflection HashCodeBuilder or EqualsBuilder in production code, I use the toHashCode (as below). I do however use the ReflectionToStringBuilder for logging and such like.

Here is an example which doesn't use reflection, but requires you to add another line when you add a field:

public int hashCode() {
  // you pick a hard-coded, randomly chosen, non-zero, odd number
  // ideally different for each class
  return new HashCodeBuilder(17, 37).
    append(foo).
    append(bar).
    toHashCode();
}

For more discussion about hashCodeBuilder, see apache commons equals/hashcode builder

Answer 2

Take a look at www.projectlombok.org as an alternative to writing these methods yourself. In particular the @Data annotation seems to fit your need, see http://www.projectlombok.org/features/Data.html.