Here is a small test from Regis:
----------
int count = 5000;
for (int i = 0; i < count; ++i) { new Date(new
java.util.Date().getTime()).toString(); }
Date date = new Date(new java.util.Date().getTime());
long start = System.currentTimeMillis();
for (int i = 0; i < count; ++i) { date.toString(); }
long end = System.currentTimeMillis();
System.out.println("Invoke Date.toString() " + count + " times, cost:
" + (end - start));
Time time = new Time(new java.util.Date().getTime());
start = System.currentTimeMillis();
for (int i = 0; i < count; ++i) { time.toString(); }
end = System.currentTimeMillis();
System.out.println("Invoke Time.toString() " + count + " times, cost:
" + (end - start));
Timestamp timestamp = new Timestamp(new java.util.Date().getTime());
start = System.currentTimeMillis();
for (int i = 0; i < count; ++i) { timestamp.toString(); }
end = System.currentTimeMillis();
System.out.println("Invoke Timestamp.toString() " + count + " times,
cost: " + (end - start));
-------------
the first loop, give time for jvm to warm up
Below data compare the two implementations:
before the patch:
Invoke Date.toString() 5000 times, cost: 6757
Invoke Time.toString() 5000 times, cost: 7699
Invoke Timestamp.toString() 5000 times, cost: 2527
after the patch:
Invoke Date.toString() 5000 times, cost: 84
Invoke Time.toString() 5000 times, cost: 95
Invoke Timestamp.toString() 5000 times, cost: 272
We can gain obvious improvement.
2008/8/28 Nathan Beyer <[EMAIL PROTECTED]>:
> Are there any associated test cases with this change? On a quick
> cursory look, I didn't see any existing tests. Did I miss them? If
> not, we need to start requiring some test cases for "simple
> improvements" like this to continue functional correctness.
>
> -Nathan
>
> On Tue, Aug 26, 2008 at 3:59 AM, <[EMAIL PROTECTED]> wrote:
>> Author: qiuxx
>> Date: Tue Aug 26 01:59:50 2008
>> New Revision: 689001
>>
>> URL: http://svn.apache.org/viewvc?rev=689001&view=rev
>> Log:
>> Apply for HARMONY-5958,([classlib][sql][performance] - improve performance
>> of java.sql.Date/Time/Timestamp.toString())
>>
>> Modified:
>>
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Date.java
>>
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Time.java
>>
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Timestamp.java
>>
>> Modified:
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Date.java
>> URL:
>> http://svn.apache.org/viewvc/harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Date.java?rev=689001&r1=689000&r2=689001&view=diff
>> ==============================================================================
>> ---
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Date.java
>> (original)
>> +++
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Date.java
>> Tue Aug 26 01:59:50 2008
>> @@ -17,8 +17,6 @@
>>
>> package java.sql;
>>
>> -import java.text.SimpleDateFormat;
>> -
>> /**
>> * A Date class which can consume and produce dates in SQL Date format.
>> * <p>
>> @@ -175,8 +173,28 @@
>> */
>> @Override
>> public String toString() {
>> - SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
>> //$NON-NLS-1$
>> - return dateFormat.format(this);
>> + StringBuilder sb = new StringBuilder(10);
>> +
>> + format((getYear() + 1900), 4, sb);
>> + sb.append('-');
>> + format((getMonth() + 1), 2, sb);
>> + sb.append('-');
>> + format(getDate(), 2, sb);
>> +
>> + return sb.toString();
>> + }
>> +
>> + private static final String PADDING = "0000"; //$NON-NLS-1$
>> +
>> + /*
>> + * Private method to format the time
>> + */
>> + private void format(int date, int digits, StringBuilder sb) {
>> + String str = String.valueOf(date);
>> + if (digits - str.length() > 0) {
>> + sb.append(PADDING.substring(0, digits - str.length()));
>> + }
>> + sb.append(str);
>> }
>>
>> /**
>>
>> Modified:
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Time.java
>> URL:
>> http://svn.apache.org/viewvc/harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Time.java?rev=689001&r1=689000&r2=689001&view=diff
>> ==============================================================================
>> ---
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Time.java
>> (original)
>> +++
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Time.java
>> Tue Aug 26 01:59:50 2008
>> @@ -17,7 +17,6 @@
>>
>> package java.sql;
>>
>> -import java.text.SimpleDateFormat;
>> import java.util.Date;
>>
>> /**
>> @@ -180,8 +179,28 @@
>> */
>> @Override
>> public String toString() {
>> - SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
>> //$NON-NLS-1$
>> - return dateFormat.format(this);
>> + StringBuilder sb = new StringBuilder(8);
>> +
>> + format(getHours(), 2, sb);
>> + sb.append(':');
>> + format(getMinutes(), 2, sb);
>> + sb.append(':');
>> + format(getSeconds(), 2, sb);
>> +
>> + return sb.toString();
>> + }
>> +
>> + private static final String PADDING = "00"; //$NON-NLS-1$
>> +
>> + /*
>> + * Private method to format the time
>> + */
>> + private void format(int date, int digits, StringBuilder sb) {
>> + String str = String.valueOf(date);
>> + if (digits - str.length() > 0) {
>> + sb.append(PADDING.substring(0, digits - str.length()));
>> + }
>> + sb.append(str);
>> }
>>
>> /**
>>
>> Modified:
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Timestamp.java
>> URL:
>> http://svn.apache.org/viewvc/harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Timestamp.java?rev=689001&r1=689000&r2=689001&view=diff
>> ==============================================================================
>> ---
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Timestamp.java
>> (original)
>> +++
>> harmony/enhanced/classlib/trunk/modules/sql/src/main/java/java/sql/Timestamp.java
>> Tue Aug 26 01:59:50 2008
>> @@ -309,62 +309,43 @@
>> @SuppressWarnings("deprecation")
>> @Override
>> public String toString() {
>> - /*
>> - * Use a DecimalFormat to lay out the nanosecond value as a simple
>> - * string of 9 integers, with leading Zeros
>> - */
>> - DecimalFormat decimalFormat = new DecimalFormat("0"); //$NON-NLS-1$
>> - decimalFormat.setMinimumIntegerDigits(9);
>> - decimalFormat.setMaximumIntegerDigits(9);
>> - String theNanos = decimalFormat.format(nanos);
>> - theNanos = stripTrailingZeros(theNanos);
>> -
>> - String year = format((getYear() + 1900), 4);
>> - String month = format((getMonth() + 1), 2);
>> - String date = format(getDate(), 2);
>> - String hours = format(getHours(), 2);
>> - String minutes = format(getMinutes(), 2);
>> - String seconds = format(getSeconds(), 2);
>> -
>> - return year + '-' + month + '-' + date + ' ' + hours + ':' + minutes
>> - + ':' + seconds + '.' + theNanos;
>> - }
>> + StringBuilder sb = new StringBuilder(29);
>>
>> - /*
>> - * Private method to format the time
>> - */
>> - private String format(int date, int digits) {
>> - StringBuilder dateStringBuffer = new
>> StringBuilder(String.valueOf(date));
>> - while (dateStringBuffer.length() < digits) {
>> - dateStringBuffer = dateStringBuffer.insert(0, '0');
>> + format((getYear() + 1900), 4, sb);
>> + sb.append('-');
>> + format((getMonth() + 1), 2, sb);
>> + sb.append('-');
>> + format(getDate(), 2, sb);
>> + sb.append(' ');
>> + format(getHours(), 2, sb);
>> + sb.append(':');
>> + format(getMinutes(), 2, sb);
>> + sb.append(':');
>> + format(getSeconds(), 2, sb);
>> + sb.append('.');
>> + if (nanos == 0) {
>> + sb.append('0');
>> + } else {
>> + format(nanos, 9, sb);
>> + while (sb.charAt(sb.length() - 1) == '0') {
>> + sb.setLength(sb.length() - 1);
>> + }
>> }
>> - return dateStringBuffer.toString();
>> +
>> + return sb.toString();
>> }
>>
>> - /*
>> - * Private method to strip trailing '0' characters from a string. @param
>> - * inputString the starting string @return a string with the trailing
>> zeros
>> - * stripped - will leave a single 0 at the beginning of the string
>> - */
>> - private String stripTrailingZeros(String inputString) {
>> - String finalString;
>> + private static final String PADDING = "000000000"; //$NON-NLS-1$
>>
>> - int i;
>> - for (i = inputString.length(); i > 0; i--) {
>> - if (inputString.charAt(i - 1) != '0') {
>> - break;
>> - }
>> - /*
>> - * If the string has a 0 as its first character, return a string
>> - * with a single '0'
>> - */
>> - if (i == 1) {
>> - return "0"; //$NON-NLS-1$
>> - }
>> + /*
>> + * Private method to format the time
>> + */
>> + private void format(int date, int digits, StringBuilder sb) {
>> + String str = String.valueOf(date);
>> + if (digits - str.length() > 0) {
>> + sb.append(PADDING.substring(0, digits - str.length()));
>> }
>> -
>> - finalString = inputString.substring(0, i);
>> - return finalString;
>> + sb.append(str);
>> }
>>
>> /**
>>
>>
>>
>
--
Best Regards
Sean, Xiao Xia Qiu
China Software Development Lab, IBM
