Print all interleavings of given two strings

Given two strings str1 and str2, write a function that prints all interleavings of the given two strings. You may assume that all characters in both strings are different

Example:

Input: str1 = "AB",  str2 = "CD"
Output:
    ABCD
    ACBD
    ACDB
    CABD
    CADB
    CDAB

Solution:

public static void interleavings(String x, String y, String r){
  if(x.length() >0){
   if(y.length() >0){
    interleavings(x.substring(1),y,r+x.charAt(0));
    interleavings(x,y.substring(1),r+y.charAt(0));
   }
   else{
    System.out.println(r+x);
   }
  }
  else{
   System.out.println(r+y);
  }
 }

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