What is the difference between the Set and Map interfaces? [closed]

The difference is the functionality defined for each of these interfaces:

• Map is an interface that defines storing objects in Key pairs (or Key) Value, where you can register, obtain and remove an item from the Key.

  Example:

  //creamos el mapa
  Map<String, Usuario> mapa = new HashMap<>();
  //agregamos elementos al mapa
  mapa.put("Luiggi Mendoza J", new Usuario(227, "Luiggi Mendoza J", 10.4k));
  mapa.put("theboshy", new Usuario(9206, "theboshy", 1));
  System.out.println(mapa.get("theboshy")); //imprime datos de usuario
  System.out.println(mapa.get("elporfirio")); //imprime nulo
  //recorrer todas las entradas llave-valor del mapa
  //e imprimir la llave y el valor correspondiente
  for (Map.Entry<String, Usuario> entry : mapa.entrySet()) {
      System.out.printf(
          "Llave: %s. Valor: %s\n",
          entry.getKey(), entry.getValue());
  }
  

  There can only be 1 Value associated with a Key. This does not mean that there can be 1 Value associated to multiple Keys. Example:

  Map<String, String> mapa = new HashMap<>();
  mapa.put("saludo", "hola mundo");
  System.out.println(mapa.get("saludo")); //imprime 'hola mundo'
  String valor = "aloha!";
  //reemplazamos el valor de la llave "saludo"
  mapa.put("saludo", valor);
  System.out.println(mapa.get("saludo")); //imprime 'aloha!'
  //asignamos el mismo valor a una nueva llave
  mapa.put("saludo efusivo", valor);
  System.out.println(mapa.get("saludo"));
  System.out.println(mapa.get("saludo efusivo"));
  //ambas sentencias imprimieros 'aloha!'
  

• Set is an interface that defines storing objects as if it were a mathematical set. This allows you to register and remove items from this set, but does not allow to get them one by one. Set is used primarily to verify that there are no repeated objects in a collection.

  Example:

  Set<Integer> set = new HashSet<>();
  //agregamos elementos
  set.add(10);
  set.add(5);
  set.add(8);
  //podemos remover elementos
  set.remove(10);
  //pero no podemos obtener elementos, no existe un método 'get'
  //lo que si, existe un método 'contains' que permite verificar
  //si un elemento existe en el set
  if (set.contains(5)) {
      System.out.println("5 existe");
  }
  //sin embargo, se pueden recorrer todos los elementos de un set
  for (Integer elem : set) {
      System.out.println(elem);
  }
  

  It should be noted that a Set can be seen simply as a Map<Object, Boolean> , where the objects to insert in Set are the keys of the Map . This can be verified by using the method Collections#newSetFromMap(Map<E, Boolean>) .