inserting in basic sorted array

Hello I have implemented this basic program which should sort out the strings that are inserted however it somehow is failing to insert the strings . For example if I implement :

        testsort t = new testsort();
        t.i("abc");
        t.i("aab");
Can anybody see the error and help me fix this error please ?

Thank you



Here is the code :



public class testsort {

private int length;
String[] data;


   public testsort() 
   {

       length = 0;

   }

public void i(String value)
{


   data[length] = value;   
  SetSorted(data);
   length++;
}


public void SetSorted(String data[])
{


 for(int i = data.length-1; i >= 0; i--) 
 {
    for(int j = 0; j < i; j++) {
        if(data[j].compareTo(data[j + 1]) > -1) {
            String temp = data[j];
            data[j] = data[j + 1];
           data[j + 1] = temp;
        }
    }
}

for(int i = 0; i < data.length; i++) 
    {
    System.out.print(data[i] +" ");
     }



  }



}