Execution order of of static blocks in an Enum type w.r.t to constructor

Question

This is from Effective Java :

// Implementing a fromString method on an enum type
  private static final Map<String, Operation> stringToEnum
      = new HashMap<String, Operation>();

  static { // Initialize map from constant name to enum constant
    for (Operation op : values())
      stringToEnum.put(op.toString(), op);
  }

  // Returns Operation for string, or null if string is invalid
  public static Operation fromString(String symbol) {
    return stringToEnum.get(symbol);
  }

Note that the Operation constants are put into the stringToEnum map from a static block that runs after the constants have been created. Trying to make each constant put itself into the map from its own constructor would cause a compilation error. This is a good thing, because it would cause a NullPointerException if it were legal. Enum constructors aren’t permitted to access the enum’s static fields, except for compile-time constant fields. This restriction is necessary because these static fields have not yet been initialized when the constructors run.

My question is regarding the line :

"Note that the Operation constants are put into the stringToEnum map from a static block that runs after the constants have been created" .

I thought the static block gets executed before the constructor runs. The are actually executed during class load time.

What am I missing here ?

Answer 1

The static blocks execute in order of appearance (you can have multiple static blocks), when the class loader loads the class, eg. it runs before the constructor.