/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements.  See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.apache.log4j.performance;/**   This program compares the cost of creating a new StringBuffer and   converting it to a String versus keeping the same StringBuffer,   setting its size to zero and then converting it to String.   <p>The table below gives some figures.<p>   <table border="1" cellpadding="4">   <tr BGCOLOR="#33CCFF">     <th BGCOLOR="#CCCCCC" rowspan="2">Total Message length     <th colspan="2" align="center">0     <th colspan="2" align="center">1     <th colspan="2" align="center">2     <th colspan="2" align="center">4     <th colspan="2" align="center">8   </tr>   <tr BGCOLOR="#3366FF">     <td>New Buffer</td> <td>setLength</td>      <td>New Buffer</td> <td>setLength</td>     <td>New Buffer</td> <td>setLength</td>     <td>New Buffer</td> <td>setLength</td>     <td>New Buffer</td> <td>setLength</td>   </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">256    <td>33 <td>22    <td>34 <td>22   <td>34 <td>22   <td>34 <td>22    <td>33 <td>23   </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">1024    <td>58 <td>41   <td>59 <td>45   <td>59 <td>48   <td>59 <td>51    <td>60 <td>44   </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">4096    <td>146 <td>132   <td>138 <td>132   <td>144 <td>126   <td>142 <td>132   <td>136 <td>132    </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">16384    <td>617 <td>593    <td>593 <td>609   <td>601 <td>617   <td>601 <td>632    <td>593 <td>632   </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">65536    <td>3218 <td>3281   <td>3093 <td>3125    <td>3125 <td>3156   <td>3125 <td>3281    <td>3062 <td>3562   </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">262144    <td>14750 <td>15125   <td>14000 <td>15500    <td>14000 <td>16125    <td>14000 <td>18000    <td>14000 <td>21375    </tr>   <tr align="right">    <td BGCOLOR="#CCCCCC">1048576    <td>87500 <td>80000   <td>60500 <td>82000    <td>57000 <td>93000    <td>57500 <td>118500    <td>57500 <td>168500    </tr>   <caption ALIGN="BOTTOM">Performance comparisons of new buffer   creation versus setLength(0) approach for various message sizes and   secondary loop lengths.   </caption>   </table>   <p>The tests copy a message to a destination string buffer and then   copy a 256 character buffer to another buffer the number of times   as specified by the secondary loop length.   <p>The <code>setLength(0)</code> method is usually faster. However,   after copying a large string it becomes slow even when copying   small strings.   <p>This is due to a peculiarity in the <code>copy</code> method in   StringBuffer class which creates a character array of the same   length as the old buffer even if the vast majority of those   characters are unused.    <p>The tests were performed on Linux using IBM's JDK 1.1.8.   <p>The test script is a crude model of what might happen in   reality. If you remain unconvinced of its results, then please send   your alternative measurement scenario.      */public class NewVsSetLen {  static String s;  static int BIGBUF_LEN = 1048576;  static int SBUF_LEN = 256;  static int RUN_LENGTH = BIGBUF_LEN/4;  static char[] sbuf = new char[SBUF_LEN];  static char[] bigbuf = new char[BIGBUF_LEN];  {    for(int i = 0; i < SBUF_LEN; i++) {      sbuf[i] = (char) (i);    }    for(int i = 0; i < BIGBUF_LEN; i++) {      bigbuf[i] = (char) (i);    }  }  static  public   void main(String[] args) {         int t;    for(int len = SBUF_LEN; len <= BIGBUF_LEN; len*=4, RUN_LENGTH /= 4) {      System.out.println("<td>"+len+"\n");      for(int second = 0; second < 16;) {	System.out.println("SECOND loop="+second +", RUN_LENGTH="			   +RUN_LENGTH+", len="+len);	t = (int)newBuffer(len, second);	System.out.print("<td>" + t);	t = (int)setLen(len, second);	System.out.println(" <td>" + t + " \n");	if(second == 0) {	  second = 1;	} else {	  second *= 2;	}      }    }      }  static  double newBuffer(int size, int second) {        long before = System.currentTimeMillis();    for(int i = 0; i < RUN_LENGTH; i++) {      StringBuffer buf = new StringBuffer(SBUF_LEN);      buf.append(sbuf, 0, sbuf.length);      buf.append(bigbuf, 0, size);      s = buf.toString();    }    for(int x = 0; x <  second; x++) {      StringBuffer buf = new StringBuffer(SBUF_LEN);      buf.append(sbuf, 0, SBUF_LEN);      s = buf.toString();    }    return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;      }  static  double setLen(int size, int second) {    long before = System.currentTimeMillis();    StringBuffer buf = new StringBuffer(SBUF_LEN);    for(int i = 0; i < RUN_LENGTH; i++) {      buf.append(sbuf, 0, sbuf.length);      buf.append(bigbuf, 0, size);      s = buf.toString();      buf.setLength(0);    }    for(int x = 0; x < second; x++) {      buf.append(sbuf, 0, SBUF_LEN);      s = buf.toString();      buf.setLength(0);    }    return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;      }  }