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  • Using lightweight object comparison
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  • 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
  1. 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()));
    	}
    }
    
  2. 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();
    }
    
  3. 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;
    }
    
  4. Create a toString function
    public String toString() {
    	return super.toString();
    }
    
  5. 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();
      }
      
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