First Impression Is Really Important

I have attended a 3-day workshop for Oracle Coherence Product. Although I am a veteran Eclipse user, we used JDeveloper 11g Technology Preview 3 during our lab sessions. During those lab sessions, I noticed an issue related to JDeveloper. JDeveloper provides some IDE mechanisms to generate equals and hashCode methods for your classes. However, it fails to generate hashCode methods correctly when your classes contain primitive fields that need to be included in hashCode generation.

public class Foo {
	private int id;
	public int hashCode() {
		final int PRIME = 37;
		int result = 1;
		return result;
	}
}

Above is the code block I just generated using JDeveloper. Although I chose id to include when generating hashCode, it doesn’t have it. As a result, you have the same hashCode value for all your Foo objects. This is not good if you are dealing with data structures like Hashtable in your application. To generate it correctly, you simply need to convert your primitive type to its Java wrapper equivalent. After this conversion, it looks more appropriate than above:

public int hashCode() {
	final int PRIME = 37;
	int result = 1;
	result = PRIME * result + id == null) ? 0 : id.hashCode(?;
	return result;
}

In summary, I think it is really important for a new product to handle some fundamental tasks appropriately to gain acceptance by its users.