Question

JAVA

Write a method that accepts a String as an argument. The method should use recursion to display each individual character in the String. Then, modify the method you just wrote so it displays the String backwards.

The following code does not correctly display the String backwards. It merely moves the first character of the String to the end:

public static void displayCharacter(String s)
   {
       if(s.length() == 0)
           return;
       else
       {
           System.out.println(s.charAt(0));
           displayCharacter(s.substring(1));
       }
   }
  
   public static void displayCharacterReverse(String s)
   {
       if(s.length() == 0)
           return;
       else
       {
           displayCharacter(s.substring(1));
           System.out.println(s.charAt(0));
       }
   }

Answer 1

There is just a slight error in displayCharacterReverse, while recursing on the input string, displayCharacterReverse function needs to call itself and not displayCharacter.

Correct Code:

public class display_string{
public static void displayCharacter(String s){
if(s.length() == 0)
return;
else{
System.out.println(s.charAt(0));
displayCharacter(s.substring(1));
}
}
  
public static void displayCharacterReverse(String s){
if(s.length() == 0)
return;
else{
displayCharacterReverse(s.substring(1));
System.out.println(s.charAt(0));
}
}

public static void main(String a[]){
String string = new String("Hello World!");
System.out.println("Printing string : "+string);
System.out.println("Printing characters in original order:");
displayCharacter(string);
System.out.println("Printing characters in reverse order:");
displayCharacterReverse(string);
}
}

X display_string.java i public class display_string{ 2 public static void displayCharacter(String s){ 3 if(s.length() == 0) 4 return; 5 else{ 6 System.out.println(s.charAt(0)); 7 displayCharacter(s.substring(1)); 8 9 10 11 public static void displayCharacterReverse(String s){ 12 if(s.length() == 0) 13 return; 14 else{ 15 displayCharacterReverse(s.substring(1)); System.out.println(s.charAt(0)); 17 } } WN - O 16 } 18 } 19 20 21 22 23 24 25 26 public static void main(String a[]){ String string = new String("Hello world!"); System.out.println("Printing string : "+string); System.out.println("Printing characters in original order:"); displayCharacter(string); System.out.println("Printing characters in reverse order:"); displayCharacterReverse(string); 27 } 28 } 29

Execution sample:

Printing string : Hello world! Printing characters in original order: H OPP I พ 1 d ! Printing characters in reverse order: ! d i ୮ 0 W Executic OPPI