Printing all variables value from a class

Question

Hi, I have a class with information about a Person. Something like:

public class Contact {
    private String name;
    private String location;
    private String address;
    private String email;
    private String phone;
    private String fax;

    public String toString() {
        // Something here
    }
    // Getters and setters.
}

I want toString to return: this.name +" - "+ this.locations ... with every var.

I was trying to do it using reflection the way I read from this question but I can't manage to print instance vars.

Which is the correctly way to solve this?

Thanks for reading!

Answer 1

When accessing the field value, pass the instance rather than null.

Why not use code generation here? Eclipse, for example, will generate a reasoble toString implementation for you.

Answer 2

From Implementing toString:

public String toString() {
  StringBuilder result = new StringBuilder();
  String newLine = System.getProperty("line.separator");

  result.append( this.getClass().getName() );
  result.append( " Object {" );
  result.append(newLine);

  //determine fields declared in this class only (no fields of superclass)
  Field[] fields = this.getClass().getDeclaredFields();

  //print field names paired with their values
  for ( Field field : fields  ) {
    result.append("  ");
    try {
      result.append( field.getName() );
      result.append(": ");
      //requires access to private field:
      result.append( field.get(this) );
    } catch ( IllegalAccessException ex ) {
      System.out.println(ex);
    }
    result.append(newLine);
  }
  result.append("}");

  return result.toString();
}

Answer 3

Why do you want to reinvent the wheel when there are opensource that are already doing the job pretty nicely.

Both apache common-langs and spring support some very flexible builder pattern

For apache, here is how you do it reflectively

public String toString()
{
  return ToStringBuilder.reflectionToString(this);
}

Here is how you do it if you only want to print fields that you care about.

public String toString() 
{
    return new ToStringBuilder(this)
      .append("name", name
      .append("location", location)
      .append("address", address)
      .toString(); 
}

You can go as far as "styling" your print output with non-default ToStringStyle or even customizing it with your own style.

I didn't personally try spring ToStringCreator api, but it looks very similar.