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Use ArrayList instead of LinkedList for known size 

Spring JDBC unlike other modules uses LinkedList instead of ArrayList
in several places. There is a large body of evidence suggesting that on
contemporary hardware ArrayList is both faster and has less overhead
than even in degenerate cases of empty lists [3] or unknown size.

There are two places in Spring JDBC where the size of the list is known
in advance and an ArrayList of the correct final size can be created

 [1] https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8011200
 [2] http://cliffc.org/blog/2017/11/05/modern-hardware-performance-cache-lines/
 [3] https://bugs.openjdk.java.net/browse/JDK-8011200

Issue: SPR-16378
This commit is contained in:
Philippe Marschall 2018-01-14 14:18:07 +01:00 committed by Juergen Hoeller
parent c88f11f958
commit 91e39d558f
2 changed files with 7 additions and 3 deletions
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7
spring-jdbc/src/main/java/org/springframework/jdbc/core/SqlParameter.java
View File

@ -16,6 +16,7 @@
package org.springframework.jdbc.core; package org.springframework.jdbc.core;
import java.util.ArrayList;
import java.util.LinkedList; import java.util.LinkedList;
import java.util.List; import java.util.List;
@ -184,12 +185,16 @@ public class SqlParameter {
* to a List of SqlParameter objects as used in this package. * to a List of SqlParameter objects as used in this package.
*/ */
public static List<SqlParameter> sqlTypesToAnonymousParameterList(@Nullable int... types) { public static List<SqlParameter> sqlTypesToAnonymousParameterList(@Nullable int... types) {
List<SqlParameter> result = new LinkedList<>(); List<SqlParameter> result;
if (types != null) { if (types != null) {
result = new ArrayList<>(types.length);
for (int type : types) { for (int type : types) {
result.add(new SqlParameter(type)); result.add(new SqlParameter(type));
} }
} }
else {
result = new LinkedList<>();
}
return result; return result;
} }

3
spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java
View File

@ -20,7 +20,6 @@ import java.util.ArrayList;
import java.util.Collection; import java.util.Collection;
import java.util.HashSet; import java.util.HashSet;
import java.util.Iterator; import java.util.Iterator;
import java.util.LinkedList;
import java.util.List; import java.util.List;
import java.util.Map; import java.util.Map;
import java.util.Set; import java.util.Set;
@ -423,7 +422,7 @@ public abstract class NamedParameterUtils {
*/ */
public static List<SqlParameter> buildSqlParameterList(ParsedSql parsedSql, SqlParameterSource paramSource) { public static List<SqlParameter> buildSqlParameterList(ParsedSql parsedSql, SqlParameterSource paramSource) {
List<String> paramNames = parsedSql.getParameterNames(); List<String> paramNames = parsedSql.getParameterNames();
List<SqlParameter> params = new LinkedList<>(); List<SqlParameter> params = new ArrayList<>(paramNames.size());
for (String paramName : paramNames) { for (String paramName : paramNames) {
params.add(new SqlParameter( params.add(new SqlParameter(
paramName, paramSource.getSqlType(paramName), paramSource.getTypeName(paramName))); paramName, paramSource.getSqlType(paramName), paramSource.getTypeName(paramName)));