case 4:
                    String treeoutput = "",
                     arrayoutput = "",
                     hashoutput = "";
                    treeoutput = treeSet.stream().map((value) -> value.toString() + " ").reduce(treeoutput, String::concat);
                    arrayoutput = treeSet.stream().map((value) -> value.toString() + " ").reduce(arrayoutput, String::concat);
                    hashoutput = treeSet.stream().map((value) -> value.toString() + " ").reduce(hashoutput, String::concat);
                    System.out.print("Array Output: " + arrayoutput + "\n");
                    System.out.print("Tree Output: " + treeoutput + "\n");
                    System.out.print("Hash Output: " + hashoutput + "\n");
                    break;