statistics.java

来自「java编程思想第3版原代码分享是java编程思想一本好书,大家多多学习」· Java 代码 · 共 26 行

//: c11:Statistics.java
// Simple demonstration of HashMap.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import java.util.*;

class Counter {
  int i = 1;
  public String toString() { return Integer.toString(i); }
}

public class Statistics {
  private static Random rand = new Random();
  public static void main(String[] args) {
    Map hm = new HashMap();
    for(int i = 0; i < 10000; i++) {
      // Produce a number between 0 and 20:
      Integer r = new Integer(rand.nextInt(20));
      if(hm.containsKey(r))
        ((Counter)hm.get(r)).i++;
      else
        hm.put(r, new Counter());
    }
    System.out.println(hm);
  }
} ///:~