content: public class Recursion {
  
      public static void main(String[] args) {
          System.out.println("countdown");
          countdown(3);
  
          System.out.println("countup");
          countup(3);
  
          System.out.println("newLine");
          newLine();
  
          System.out.println("nLines");
          nLines(3);
  
          System.out.println("threeLine");
          threeLine();
  
          System.out.println("displayBinary");
          displayBinary(23);
          System.out.println();
      }
  
      public static void countdown(int n) {
          if (n == 0) {
              System.out.println("Blastoff!");
          } else {
              System.out.println(n);
              countdown(n - 1);
          }
      }
  
      public static void newLine() {
          System.out.println();
      }
  
      public static void threeLine() {
          newLine();
          newLine();
          newLine();
      }
  
      public static void nLines(int n) {
          if (n > 0) {
              System.out.println();
              nLines(n - 1);
          }
      }
  
      public static void forever(String s) {
          System.out.println(s);
          forever(s);
      }
  
      public static void countup(int n) {
          if (n == 0) {
              System.out.println("Blastoff!");
          } else {
              countup(n - 1);
              System.out.println(n);
          }
      }
  
      public static void displayBinary(int value) {
          if (value > 0) {
              displayBinary(value / 2);
              System.out.print(value % 2);
          }
      }
  
  }
  