Call the static method PressAnykey to keep to "DOS" window open.

 import java.io.*;

public class IO {
  
  public static void PressAnyKey() {

    BufferedReader input = 
      new BufferedReader(new InputStreamReader(System.in));

    System.out.print("Press any key...");

    try { 
  input.readLine();
    }
    catch (Exception e) { 
  e.printStackTrace();
    }

  }
}

For example

 public class HelloWorld {

   public static void main(String[] args) {

      System.out.println("Hello world.");
      IO.PressAnyKey();    
   
   }
}