String attribute in class that can only assign to specific values-CodePudding

I remember that there is a data structure that guarantees that a certain string can only receive specific values, it works like an interface or something. I don't remember exactly the name of this data structure and couldn't find it easily.

Let me try to explain the context.

Let's say I've got a class called Foo with the parameter position.

Class Foo {
   public static final String TOP = "TOP";
   public static final String BOTTOM = "BOTTOM";
   public static final String MIDDLE = "MIDDLE";

   private String position;

   Foo(String position){
        this.position = position;
   }
}

If I assign to position the values TOP, BOTTOM or Middle, position is going to accept. If I assign another value it will throw an exception.

new Foo(Foo.TOP)         // OK
new Foo(Foo.MIDDLE)      // OK
new Foo(Foo.BOTTOM)      // OK
new Foo("anystring")     // Throws Exception.

I know I could do a simple if else or switch and throw an exception, but I'd like to find this specific data structure.

CodePudding user response：

You should use enum for this to solve at that way.

Class Foo {
   public static enum Position {TOP, BOTTOM, MIDDLE};

   private Position position;

   Foo(String position){
        this.position = Position.valueOf(position);
   }
}

But keep in mind: enum is not a String. But on enum you can call toString(), and also can parse a String to enum, like I did.