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JBEL is a small, efficient Java library enabling programmers to create simple, easily understandable expressions to perform collection filtering and/or sorting. The following benefits are realized through consistent use of JBEL:

No more cut-n-paste coding for comparing and filtering.
Reduce duplicated code and code size.
Improve filter and sort clarity and readability.
Increase application reliability by reducing bug introduction.

The following examples should get you going on your understanding and justification for use of JBEL. After a look, the benefits are obvious, especially when considering the amount of cut-n-paste coding that often happens around comparing and filtering.

Filtering

Before JBEL:

After JBEL:

private Collection filterCollection(Collection toFilter)

{
  Collection results = new Vector();
  Iterator iterator = toFilter.iterator();

  while (iterator.hasNext())
  {
    (SomeInstance) instance = (SomeInstance) iterator.next();

    if (instance.getAccountBalance() > 10000
        && instance.isNewCustomer())
    {
      results.add(instance);
    }
  }

  return results;
}

Collection results = filterCollection(toFilter);

SelectExpressionBuilder builder = new SelectExpressionBuilder();
builder.attribute("accountBalance").greaterThan(10000)
  .and(builder.attribute("isNewCustomer").equalTo(true));

Collection results = Expressions.select(toFilter, builder.getExpression());

Sorting

Before JBEL:

After JBEL:

public class PersonNameComparator
implements Comparator
{
  public int compare(Object obj1, Object obj2)
  {
    Person person1 = (Person) obj1;
    Person person2 = (Person) obj2;
    int result = person1.getLastName()
      .compareTo(person2.getLastName());

    if (result == 0)
    {
      result = person1.getFirstName()
        .compareTo(person2.getFirstName());
    }

    if (result == 0)
    {
      result = person1.getMiddleInitial()
        .compareTo(person2.getMiddleInitial());
    }

    return result;
  }
}

Collections.sort(peopleToSort, new PersonNameComparator());

OrderByExpressionBuilder
orderBy = new OrderByExpressionBuilder();
orderBy.attribute("lastName")
  .attribute("firstName")
  .attribute("middleInitial");

Collections.sort(peopleToSort, orderBy.getExpression());