springdetector.java

Java编程思想 第九课 全源码

//: c09:SpringDetector.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Looks plausible, but doesn't work.
import java.util.*;

class Groundhog {
  int ghNumber;
  Groundhog(int n) { ghNumber = n; }
}

class Prediction {
  boolean shadow = Math.random() > 0.5;
  public String toString() {
    if(shadow)
      return "Six more weeks of Winter!";
    else
      return "Early Spring!";
  }
}

public class SpringDetector {
  public static void main(String[] args) {
    HashMap hm = new HashMap();
    for(int i = 0; i < 10; i++)
      hm.put(new Groundhog(i), new Prediction());
    System.out.println("hm = " + hm + "\n");
    System.out.println(
      "Looking up prediction for Groundhog #3:");
    Groundhog gh = new Groundhog(3);
    if(hm.containsKey(gh))
      System.out.println((Prediction)hm.get(gh));
    else
      System.out.println("Key not found: " + gh);
  }
} ///:~