calculating the percentile in java

1/**
2 * A simple method to log 95th percentile information
3 */
4private static void logPercentileInfo() {
5
6    double total = 0;
7    for (Map.Entry<Long, Long> entry : CassandraTimer.histogram.entrySet()) {
8        long value = entry.getKey() * entry.getValue();
9        total += value;
10    }
11
12    double sum = 0.95*total;
13
14    double totalSum = 0;
15
16    SortedSet<Long> keys = new TreeSet<Long>(CassandraTimer.histogram.keySet());
17    for (long key : keys) {
18
19        totalSum += CassandraTimer.histogram.get(key);
20
21        if(totalSum >= sum) {
22           //this is the 95th percentile I guess
23            System.out.println(key);
24        }
25    }
26
27}

1for (i=0, sum=0; i<n; i++) sum += Number[i];
2tot = sum;
3for (i=0, sum=0; i<n && sum < 0.95*tot; i++) sum += Number[i];
4// i is about it

1  public static long[] percentiles(long[] latencies, double... percentiles) {
2    Arrays.sort(latencies, 0, latencies.length);
3    long[] values = new long[percentiles.length];
4    for (int i = 0; i < percentiles.length; i++) {
5      int index = (int) (percentiles[i] * latencies.length);
6      values[i] = latencies[index];
7    }
8    return values;
9  }