Using lightweight object comparison - WG: Programmer's Cafe

Using the Apache commons lang can be slow for large scale object comparisons (like sorts) so a faster method is to use something like what is shown below
Note: All code below should go in the object or object implementation

Create an equals function

public boolean equals(Object obj) {
	if (null == obj) return false;
	if (!(obj instanceof org.sakaiproject.tool.mytool.MyObject)) return false;
	else {
		org.sakaiproject.tool.mytool.MyObject castObj = 
			(org.sakaiproject.tool.mytool.MyObject) obj;
		if (null == this.getId() || null == castObj.getId()) return false;
		else return (this.getId().equals(castObj.getId()));
	}
}

Create a hashCode function

public int hashCode() {
	if (null == this.getId()) return Integer.MIN_VALUE;
	String hashStr = this.getClass().getName() + ":" + this.getId().hashCode();
	return hashStr.hashCode();
}

Create a compareTo function

public int compareTo(Object obj) {
	if (obj.hashCode() > hashCode()) return 1;
	else if (obj.hashCode() < hashCode()) return -1;
	else return 0;
}

Create a toString function

public String toString() {
	return super.toString();
}

Your object should now be comparable to objects of the same type that have the same data

Safer comparisons should be done using the commons-lang package - Using commons lang for object comparison
A sample of an object which demostrates use of the lightweight comparisons: TaskImpl.java

A sample of implemented functions using the lightweight method:

public boolean equals(Object obj) {
	if (null == obj) return false;
	if (!(obj instanceof Task)) return false;
	else {
		Task castObj = (Task) obj;
		if (null == this.getId() || null == castObj.getId()) return false;
		else return (this.getId().equals(castObj.getId()));
	}
}

public int hashCode() {
	if (null == this.getId()) return super.hashCode();
	String hashStr = this.getClass().getName() + ":" + this.getId().hashCode();
	return hashStr.hashCode();
}

public int compareTo(Object obj) {
	if (obj.hashCode() > hashCode()) return 1;
	else if (obj.hashCode() < hashCode()) return -1;
	else return 0;
}

public String toString() {
	return super.toString();
}