Counter抽象数据类型的实现

古城微笑少年丶 2021-07-24 15:09 420阅读 0赞

**一 代码**

package Counter;
    
    import common.StdOut;
    import common.StdRandom;
    
    public class Counter implements Comparable<Counter> {
        private final String name;     // counter name
        private int count = 0;         // current value
    
        public Counter(String id) {
            name = id;
        }
    
        public void increment() {
            count++;
        }
    
        public int tally() {
            return count;
        }
    
        public String toString() {
            return count + " " + name;
        }
    
        @Override
        public int compareTo(Counter that) {
            if      (this.count < that.count) return -1;
            else if (this.count > that.count) return +1;
            else                              return  0;
        }
    
        public static void main(String[] args) {
            int n = Integer.parseInt(args[0]);
            int trials = Integer.parseInt(args[1]);
    
    
            // create n counters
            Counter[] hits = new Counter[n];
            for (int i = 0; i < n; i++) {
                hits[i] = new Counter("counter" + i);
            }
    
            // increment trials counters at random
            for (int t = 0; t < trials; t++) {
                hits[StdRandom.uniform(n)].increment();
            }
    
            // print results
            for (int i = 0; i < n; i++) {
                StdOut.println(hits[i]);
            }
        }
    }

**二 测试结果**

F:\Algorithm\target\classes>java Counter.Counter 6 10000
    1634 counter0
    1632 counter1
    1669 counter2
    1674 counter3
    1699 counter4
    1692 counter5

**三 说明**

原始数字类型的实例变量默认值为0，布尔类型变量为false，引用类型变量为null。

抽象数据类型三步走：

1 定义一份API。

2 用一个Java类实现API的定义。

3 实现多个测试用例来验证前两步做出的设计决定。

**四 一个简单计数器的抽象数据类型**

<table> 
 <tbody> 
  <tr> 
   <td colspan="2"> <p>public class Counter</p> </td> 
  </tr> 
  <tr> 
   <td> <p>Counter(String id)</p> </td> 
   <td> <p>创建一个名为id的计数器</p> </td> 
  </tr> 
  <tr> 
   <td> <p>public void increment()</p> </td> 
   <td> <p>将计数器的值加1</p> </td> 
  </tr> 
  <tr> 
   <td> <p>public int tally()</p> </td> 
   <td> <p>计数器的值</p> </td> 
  </tr> 
  <tr> 
   <td> <p>public String toString()</p> </td> 
   <td> <p>对象的字符串表示</p> </td> 
  </tr> 
 </tbody> 
</table>

**五 典型用例**

public class Flips {
        public static void main( String[] args ) {
            int T = Integer.parseInt(args[0]);
            Counter heads = new Counter("heads");
            Counter tails = new Counter("tails");
            for (int t = 0;t<T;t++){
                if(StdRandom.bernoulli(0.5)){
                    heads.increment();
                }else {
                    tails.increment();
                }
            }
            StdOut.println(heads);
            StdOut.println(tails);
            StdOut.println("delta:"+Math.abs(heads.tally()-tails.tally()));
        }
    }

**六 数据类型的实现**

public class Counter {
        private final String name;     // counter name
        private int count = 0;         // current value
    
        public Counter(String id) {
            name = id;
        }
    
        public void increment() {
            count++;
        }
    
        public int tally() {
            return count;
        }
    
        public String toString() {
            return count + " " + name;
        }
    }

**七 使用方法**

F:\Algorithm\target\classes>java Flips.Flips 1000000
    499336 heads
    500664 tails
    delta:1328

**八 代码参考**

[https://gitee.com/cakin24/Algorithm][https_gitee.com_cakin24_Algorithm]

[https_gitee.com_cakin24_Algorithm]: https://gitee.com/cakin24/Algorithm