Package com.clearspring.analytics.util

Source Code of com.clearspring.analytics.util.ObyCount

/*
* Copyright (C) 2011 Clearspring Technologies, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.clearspring.analytics.util;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import com.clearspring.analytics.stream.cardinality.AdaptiveCounting;
import com.clearspring.analytics.stream.cardinality.ICardinality;


/**
* Simple cardinality estimation command line utility
*
* Usage:
* > obycount [update-rate]
*
* update-rate: output results after every update-rate elements/lines
*
* Example:
* > cat elements.txt | obycount 
*
*/
public class ObyCount
{
    public static void usage()
    {
        System.err.println
        (
                "obycount [update-rate]\n" +
                "\n" +
                "update-rate: output results after every update-rate elements/lines" +
                "\n" +
                "Example:" +
                "> cat elements.txt | obycount" +
                "\n"
        );
       
        System.exit(-1);
    }
   
    public static void main(String[] args) throws IOException
    {
        long updateRate = -1;
        long count = 0;
               
        if(args.length > 0)
        {
            try
            {
                updateRate = Long.parseLong(args[0]);
            }
            catch(NumberFormatException e)
            {
                System.err.print("Bad update rate: '"+args[0]+"'  Update rate must be an integer.");
                usage();
            }
        }
       
        ICardinality card = AdaptiveCounting.Builder.obyCount(Integer.MAX_VALUE).build();
       
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

        String line = null;
        while((line = in.readLine()) != null)
        {           
            card.offer(line);
            count++;
           
            if(updateRate > 0 && count % updateRate == 0)
            {
                System.out.println(formatSummary(count, card.cardinality()));
            }
        }
       
        System.out.println(formatSummary(count, card.cardinality()));               
    }      
   
    protected static String formatSummary(long count, long cardinality)
    {
        String cntStr = Long.toString(count);
        int len = cntStr.length();
        int l1 = Math.max(len,10);
        int l2 = Math.max(len, 20);
        String fmt = "%"+l1+"s %"+l2+"s";
        StringBuilder sb = new StringBuilder();
        sb.append(String.format(fmt, "Item Count", "Cardinality Estimate")).append('\n');
        sb.append(String.format(fmt, TopK.string('-', l1), TopK.string('-', l2))).append('\n');
        sb.append(String.format(fmt, count, cardinality)).append('\n');
        return sb.toString();
    }
}
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