Question

So I have a class in java which I group variables together to create my object like so:

public class ExampleClass
{
    private String name;
    private String test;
    private int etc;

    public ExampleClass()
    {
    }

    public String getName()
    {
        return name;
    }

    public void setName(String newName)
    {
        name = newName;
    }

    // ... 
}

Then I create an array or list of these objects, but for this question we will say an array:

int counter = 10;
ExampleClass e[] = new ExampleClass[counter];

for(int i = 0; i < counter; i++)
{
    ExampleClass e2 = ExampleClass();
    e2.setName("a name"); // string grabbed from some other source...
    // ...

    e[i] = e2;
}

And then I fill the values with data which can be anything. Now my question is, how can I sort my array (or list) by alphabetical order of one of the variables, such as name? I’ve used Arrays.sort(theArray) before for when it’s a String[] but I can’t quite work out how to do this with my custom class.

Just to note, this is all in java for the Android but the platform shouldn’t matter.

Answer 1

You can create a Comparator for your ExampleClass and use SortedSet to keep your objects in. In this way your objects will always be sorted. For example,

public class EComparator implements Comparator<ExampleClass> {

  public int compare(ExampleClass o1, ExampleClas o2) {
    return o1.getName().compareTo(o2.getName);
  }

}

And then use TreeSet to auto-sort your examples:

SortedSet<ExampleClass> data = new TreeSet<ExampleClass>(new EComparator());
data.add(e1);
data.add(e2);
data.add(e3);
data.add(e4);