Ron’s Weblog

One of my favorite open source libraries is the Jakarta commons. I find myself using some methods and classes all the time. The top few, based on how often they appear in my code, are:

1. StringUtils (org.apache.commons.lang)

   StringUtils.isNotEmpty(str): Sure beats having to do the following:

   if(str!= null && str.length() >0) {
        ----
   }

   This can be expressed simply as:

   if(StringUtils.isNotEmpty(str)){
      ----
   }

   StringUtils.isEmpty(str), StringUtils.isBlank(str), StringUtils.isNotBlank (str) have similar semantics, with intuitive handling of “null” variables.
   Check out the API docs for more time-savers.

2. ToStringBuilder (org.apache.commons.lang.builder)

   Like most others, I find it invaluable to have a well defined toString method in every class I write. This is especially true of stateful classes(domain objects, DTOs etc).
   It is painful to write code like:

   public String toString() {
       StringBuffer buffer = new StringBuffer();
       buffer.append("Last Name=").append(lastName);
       buffer.append("First Name=").append(firstName);
   }

   The quick and easy:

      return ToStringBuilder.reflectionToString(this);

   If you want to customize which fields are included/excluded, it’s still simpler than using StringBuffer:

      return new ToStringBuilder(this).
          append("firstName",this.firstName).
          append("lastName",this.lastName).toString();

   Note: There are many options available like changing the default output format, including the superclass etc. Check out the API for more details.

3. EqualsBuilder and HashCodeBuilder (org.apache.commons.lang.builder)

   Again, a really simple way to write good equals andhashCode methods:

   public boolean equals(Object other) {
      return EqualsBuilder.reflectionEquals(this, other);
   }
   public int hashCode() {
       return HashCodeBuilder.reflectionHashCode(17,37,this);
   }

   See Also: CompareToBuilder

4. Validate (org.apache.commons.lang)

   A good practice is to always ensure that arguments to a method call are correct. For example,

      public void doSomething(Long aLong, Collection aCollection){
         if(aLong == null) {
             throw new IllegalArgumentException("aLong is null");
      }
   
      if(aCollection == null  || aCollection.isEmpty()) {
         throw new IllegalArgumentException(  "aCollection is null or empty");
      }
      ---
   }

   This can be expressed more concisely:

   public void doSomething(Long aLong, Collection aCollection){
     Validate.notNull(aLong, "aLong is null");
     Validate.notEmpty(aCollection, "aCollection is null or empty");
      -----
   }

The above mentioned are but a few of the useful and elegant methods on the commons lang API. The web site is http://jakarta.apache.org/commons/lang/