Question

I have a method that generates pop-up menu with many submenus. Basically these menus given dynamically so I have to have algorithm to handle creating submenus using below string.
In order to do it I will need to transform this string into Java Tree by splitting using the delimiter. I am stuck on how to handle splitted string data and translate to the Java Tree Model according to Parent and children nodes.

An Example of Dynamic String Values that I need to parse:

String str = ” Menu1; Menu2; [Menu2A; Menu2B; [Menu2B-A; Menu2B-B];]; Menu3; “;

After Handling operation The output should be:

                                 Pop-up Menu
                                 /    |     \
                           Menu1    Menu2   Menu3
                                 /     | 

                              Menu2A     Menu2B
                                          |       \
                                          |        \
                                       Menu2B-A  Menu2B-B

Answer 1

You could do something like:

• Traverse the string from left to right, collecting characters into a current string variable.
• If you encounter a ; put the current string in a data structure holding (level, array of menu entries for level).
• If you encounter a [ call recursively with the rest of the string and level + 1.
• If you encounter a ] return.

Some approximate Java code:

private int parseString(String input, String parent, 
                        Map<String, ArrayList<String>> levels) {

     StringBuilder currentString = new StringBuilder();
     int index = 0;
     while(index < input.length()) {
         char c = input.charAt(index);

         if(c == ' ') { // ignore spaces
             index++;
             continue;
         }

         if(c == ';') { // end of menu entry, add to the list
             if(!currentString.toString().isEmpty()) {
                 levels.put(currentString.toString(), new ArrayList<String>());             
                 levels.get(level).add(currentString.toString());
             }
             currentString.delete(0, currentString.length());
             index++;
             continue;
         }

         if(c == ']') { // end of sublist, return
             return index + 1;
         }

         if(c == '[') { // start of sublist, recursive call
             int temp = parseString(input.substring(index + 1), 
                                    levels.get(parent).get(levels.get(parent).size() - 1), levels);
             index += temp;
             index++;
             continue;
         }

         currentString.append(c);
         index++;             
     }
     return 0;
}