Google Guava Quickie: Clean toString methods

July 24, 2012 | 2 min Read

I’m not very good at debugging code. This is the result of a test infection :). When you do test driven development you don’t need to debug very often. But there are rare cases when I need to start the Debugger. For this task, I love to be able to see speakable representations of the objects in the current scope when it stops at a breakpoint. When I do Java development within Eclipse this can be easily achieved using a Detail Formatter which can be added in the Variables View.

As a result, there is almost no need for me to implement the toString method of an object. But there is one exception. In concurrent environments where I can’t use the debugger effectively I often go back to old school debugging aka. System.out.println(). When using this I don’t want to spend too much time implementing the toString method of an object. I would like to see speakable representations of my objects without implementing a format on my own. The good news is that Google Guava provides a little helper for this that you might not have heard about.  It can be found in the [Objects]( class of the base package. Let’s take a look at a toString implementation using Guava’s toStringHelper for the Fruit Class from the last post.

public class Fruit {
  private String name;
  private String family;
  private int calories;
  public String toString() {
    return Objects.toStringHelper( getClass() )
      .add( "Name", name )
      .add( "Family", family )
      .add( "Calories", calories )

Instead of using a StringBuilder or other ugly concatenation methods we can simply call Objects.toStringHelper and add as many arguments as we want. The output looks like this:

Fruit{Name=A name, Family=A family, Calories=12345}

As the title of this post said, this is really just a quickie, but a useful one from my point of view  ;)

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