What will be the output of the program?

public class SyncTest 
 {     public static void main (String [] args)    
       {     
          Thread t = new Thread()           
          { 
             Foo f = new Foo();             
             public void run()              
             {                 
                f.increase(20);             
             }     
          };    
       t.start();     
        }
     } 
     class Foo 
     {   
        private int data = 23;   
        public void increase(int amt)      
        {  
             int x = data;  
             data = x + amt;    
        }
     } 

and assuming that data must be protected from corruption, what€”if anything€”can you add to the preceding code to ensure the integrity of data?