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 @Immutable
 public final class Point {
   private final int f_x;
   private final int f_y;

   public Point(int x, int y) {
     f_x = x;
     f_y = y;
   }

   public int getX() {
     return f_x;
   }

   public int getY() {
     return f_y;
   }
 }

According to Joshua Bloch [Bloch 2008],

It is not necessary to document the immutability of enum types. Unless it is obvious from the return type, static factories must document the thread safety of the returned object, as demonstrated by Collections.synchronizedMap.

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It is important to document all the locks that are being used to protect shared state. According to Brian Goetz and colleagues [Goetz 2006a],

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Documenting Thread-Confinement Policies

Dean Sutherland and William Scherlis propose annotations that can document thread-confinement policies. Their approach allows verification of the annotations against as-written code [Sutherland 2010].

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