Java中EnumSet代替位域代码详解

//Bit field enumeration constant - OBSOLETE
public class Test {
  public static final byte STYLE_BOLD     = 1<<0; // 1
  public static final byte STYLE_ITALIC    = 1<<1; // 2
  public static final byte STYLE_UNDERLINE   = 1<<2; // 4
  public static final byte STYLE_STRIKETHROUGH = 1<<3; // 6

  //Parameter is bitwise OR of zero or more STYLE_ constants
  public void applyStyles(int styles) { ... }
}

//EnumSet - a modern replacement for bit fields
public class Text {
  public enum Style { BOLD, ITALIC, UNDERLINE, STRIKETHROUGH };

  //Any Set could be passed in, but EnumSet is clearly best
  public void applyStyles(Set<Style> styles) { 
    System.out.println(styles);
  }

  public void test() {
    applyStyles(EnumSet.of(Style.BOLD, Style.ITALIC));
  }
}

public void test() {
  EnumSet<Style> styles = EnumSet.of(Style.BOLD, Style.ITALIC);
  Set<Style> unmodifiableStyle = Collections.unmodifiableSet(styles);
  unmodifiableStyle.add(Style.UNDERLINE);
}