securitycategory.java

来自「Thinking in JAVA第四版源代码」· Java 代码 · 共 38 行

//: enumerated/SecurityCategory.java
// More succinct subcategorization of enums.
import net.mindview.util.*;

enum SecurityCategory {
  STOCK(Security.Stock.class), BOND(Security.Bond.class);
  Security[] values;
  SecurityCategory(Class<? extends Security> kind) {
    values = kind.getEnumConstants();
  }
  interface Security {
    enum Stock implements Security { SHORT, LONG, MARGIN }
    enum Bond implements Security { MUNICIPAL, JUNK }
  }
  public Security randomSelection() {
    return Enums.random(values);
  }
  public static void main(String[] args) {
    for(int i = 0; i < 10; i++) {
      SecurityCategory category =
        Enums.random(SecurityCategory.class);
      System.out.println(category + ": " +
        category.randomSelection());
    }
  }
} /* Output:
BOND: MUNICIPAL
BOND: MUNICIPAL
STOCK: MARGIN
STOCK: MARGIN
BOND: JUNK
STOCK: SHORT
STOCK: LONG
STOCK: LONG
BOND: MUNICIPAL
BOND: JUNK
*///:~