I was wondering if there is a way or a library I can use to do the following:

I have an arraylist of objects where each obj has a name.

The list needs to always be unique with a maximum of 5 elements like [E1,E2,E3]

If for example the list has initial form [E3,E5] and I add an object, its name should be E1 and the list will be [E1,E3,E5] or [E3,E5,E1] it doesn't matter, as long as the name is unique and the item is added to the list starting from 1 to 5.

If add another item, it should be [E3,E5,E1,E2], always a unique name and between 1 and 5

These are my failed attempts,

StartNode node = new StartNode();
node.setName("E1");

for (int i = 0; i < circuit.getNbStartNodes(); i  ) {
    for (int j = 1; j <= circuit.getNbStartNodes(); j  ) {
        String test = ((StartNode) circuit.getStartNode(j)).getName();
        if (("E" j).equalsIgnoreCase(test) && ("E" j).equalsIgnoreCase(node.getName()) ) {
            break;
        }
        else
            node.setName("E"   j);
    }
}

/*while (t <= circuit.getNbStartNodes()) {
      for (int j = 0; j < circuit.getNbStartNodes(); j  ) {
          String test = ((StartNode) circuit.getStartNode(j)).getName();
          if (("E"   t).equalsIgnoreCase(test) || ("E"   t).equalsIgnoreCase(node.getName()))
              break;
          else {
              node.setName("E"   t);
          }
      }
      t  ;
  }
*/

/*  for (int i = 1; i <= circuit.getNbStartNodes(); i  ) {
        for (int j = 0; j < circuit.getNbStartNodes(); j  ) {
            String test = ((StartNode) circuit.getStartNode(j)).getName();
            if (!("E"   i).equalsIgnoreCase(test)) {
                node.setName("E"   i);
                t=0;
                break;
            }
        }
        if (t==0)
            break;
        else
            continue;
*/
//String test = ((StartNode) circuit.getStartNode(i)).getName();
//for (int j = 1; j <= circuit.getNbStartNodes(); j  ) {
//    if (!("E"   j).equalsIgnoreCase(test))
//       node.setName("E"   j);
//}

What did I do wrong in my code?

CodePudding user response：

• Create a small boolean array to track which names are already used and populate it with accordingly
• Find the first unused element and use it as id.

boolean[] used = new boolean[circuit.getNbStartNodes()];

for (int i = 0; i < used.length; i  ) {
    int index = Integer.parseInt(((StartNode) circuit.getStartNode(j)).getName().substring(1)) - 1; // should be   in range 0..4
    used[index] = true;
}

String name = "E";
for (int i = 0; i < used.length; i  ) {
    if (!used[i]) {
        name  = String.valueOf(i   1); // starting from 1
        break;
    }
}
System.out.println("free name: "   name);
StartNode node = new StartNode();
node.setName(name);

// add new node to circuit, etc.