Java这个关键字

public class Tester {

   private String message;

   public Tester(String message){

      this.message = message;

   }

   public void printMessage(){

      System.out.println(message);

   }

   public static void main(String args[]) {

      Tester tester = new Tester("Hello World");

      tester.printMessage();

   }

}