1.程式碼

import java.io.Serializable;
import java.util.NavigableMap;
import java.util.Random;
import java.util.TreeMap;

public class Zifp_gen implements Serializable {
    private Random random = new Random(0);
    NavigableMap<Double, Integer> map;
    private static final double Constant = 1.0
 
;
   
    public  Zifp_gen(int nums, double skewness) {
        // create the TreeMap
        map = computeMap(nums, skewness);
    }
    //size為rank個數，skew為資料傾斜程度, 取值為0表示資料無傾斜，取值越大傾斜程度越高
    private static NavigableMap<Double, Integer> computeMap(
            int size, double skew) {
        NavigableMap
 
<Double, Integer> map =
                new TreeMap<Double, Integer>();
        //總頻率
        double div = 0;
        //對每個rank，計算對應的詞頻，計算總詞頻
        for (int i = 1; i <= size; i++) {
            //the frequency in position i
            div += (Constant / Math.pow(i, skew));
        }
        
 
//計算每個rank對應的y值，所以靠前rank的y值區間遠比後面rank的y值區間大
        double sum = 0;
        for (int i = 1; i <= size; i++) {
            double p = (Constant / Math.pow(i, skew)) / div;
            sum += p;
            map.put(sum, i - 1);
        }
        return map;
    }

//    public int next() {         // [1,n]
//        double value = random.nextDouble();
//        //找最近y值對應的rank
//        return map.ceilingEntry(value).getValue() + 1;
//    }

}

2.test

import java.util.NavigableMap;

public class Test {
    public static void main(String args[]){
        Zifp_gen z1=new Zifp_gen(100,1.0);
        for (NavigableMap.Entry<Double, Integer> entry : z1.map.entrySet()) {
            System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
        }
    }
  }