Effective Java! Use EnumSet Instead of Bit Fields

Sometimes when we have an enumerated type that is primarily used in sets developers will set each value as an int or long with each being a different power of two. Something like the following:

public class TextStyles {
  public static final int STYLE_BOLD = 1 << 0; // 1
  public static final int STYLE_ITALIC = 1 << 1; // 2
  public static final int STYLE_UNDERLINE = 1 << 2; // 4
  public static final int STYLE_STRIKETHROUGH = 1 << 3; // 8
  public void applyStyles(int styles) { ... }
}

This class can then be used using bitwise ORs to combine styles. For example:

text.applyStyles(TextStyles.STYLE_BOLD | TextStyles.STYLE_UNDERLINE);

We can also perform union and intersection operations with this setup. It also proves to be very space efficient. All of this being said, this system suffers from the same issues that we discussed in the previous chapter. While debugging this system likely suffers from even further confusion as figuring out the current state of the variables requires considering the bits of each value. Another thing that we need to consider is how many enumerated types we will ever need to determine if we need an int or long. If we need to change this type later it is difficult to change the API throughout the system.

There is a better way built into the java.util package in the form of the EnumSet class. This class implements the Set interface with all of it's richness, type safety, and…