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## org.apache.log4j.performance
Class NewVsSetLen

    java.lang.Object
      |
      +--org.apache.log4j.performance.NewVsSetLen

public class NewVsSetLen
extends Object

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.

The table below gives some figures.

Total Message length | 0 | 1 | 2 | 4 | 8
--- | --- | --- | --- | --- | ---
New Buffer | setLength | New Buffer | setLength | New Buffer | setLength | New Buffer | setLength | New Buffer | setLength
256 | 33 | 22 | 34 | 22 | 34 | 22 | 34 | 22 | 33 | 23
1024 | 58 | 41 | 59 | 45 | 59 | 48 | 59 | 51 | 60 | 44
4096 | 146 | 132 | 138 | 132 | 144 | 126 | 142 | 132 | 136 | 132
16384 | 617 | 593 | 593 | 609 | 601 | 617 | 601 | 632 | 593 | 632
65536 | 3218 | 3281 | 3093 | 3125 | 3125 | 3156 | 3125 | 3281 | 3062 | 3562
262144 | 14750 | 15125 | 14000 | 15500 | 14000 | 16125 | 14000 | 18000 | 14000 | 21375
1048576 | 87500 | 80000 | 60500 | 82000 | 57000 | 93000 | 57500 | 118500 | 57500 | 168500
Performance comparisons of new buffer creation versus setLength(0) approach for various message sizes and secondary loop lengths.

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.

The `setLength(0)` method is usually faster. However, after copying a large string it becomes slow even when copying small strings.

This is due to a peculiarity in the `copy` 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.

The tests were performed on Linux using IBM's JDK 1.1.8.

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.

Constructor Summary
`NewVsSetLen()`

Method Summary
`static void` | `main(String[] args)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### NewVsSetLen

    public NewVsSetLen()

Method Detail

### main

    public static void main(String[] args)

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Copyright 2000-2005 Apache Software Foundation.