From 91e39d558f1a95bd1a49f29e9636135085bc628f Mon Sep 17 00:00:00 2001
From: Philippe Marschall <philippe.marschall@gmail.com>
Date: Sun, 14 Jan 2018 14:18:07 +0100
Subject: [PATCH] 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
---
 .../java/org/springframework/jdbc/core/SqlParameter.java   | 7 ++++++-
 .../jdbc/core/namedparam/NamedParameterUtils.java          | 3 +--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/spring-jdbc/src/main/java/org/springframework/jdbc/core/SqlParameter.java b/spring-jdbc/src/main/java/org/springframework/jdbc/core/SqlParameter.java
index 2a6a792540..f182ed42a1 100644
--- a/spring-jdbc/src/main/java/org/springframework/jdbc/core/SqlParameter.java
+++ b/spring-jdbc/src/main/java/org/springframework/jdbc/core/SqlParameter.java
@@ -16,6 +16,7 @@
 
 package org.springframework.jdbc.core;
 
+import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
 
@@ -184,12 +185,16 @@ public class SqlParameter {
 	 * to a List of SqlParameter objects as used in this package.
 	 */
 	public static List<SqlParameter> sqlTypesToAnonymousParameterList(@Nullable int... types) {
-		List<SqlParameter> result = new LinkedList<>();
+		List<SqlParameter> result;
 		if (types != null) {
+			result = new ArrayList<>(types.length);
 			for (int type : types) {
 				result.add(new SqlParameter(type));
 			}
 		}
+		else {
+			result = new LinkedList<>();
+		}
 		return result;
 	}
 
diff --git a/spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java b/spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java
index d1dcb94795..92863785d0 100644
--- a/spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java
+++ b/spring-jdbc/src/main/java/org/springframework/jdbc/core/namedparam/NamedParameterUtils.java
@@ -20,7 +20,6 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.Iterator;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -423,7 +422,7 @@ public abstract class NamedParameterUtils {
 	 */
 	public static List<SqlParameter> buildSqlParameterList(ParsedSql parsedSql, SqlParameterSource paramSource) {
 		List<String> paramNames = parsedSql.getParameterNames();
-		List<SqlParameter> params = new LinkedList<>();
+		List<SqlParameter> params = new ArrayList<>(paramNames.size());
 		for (String paramName : paramNames) {
 			params.add(new SqlParameter(
 					paramName, paramSource.getSqlType(paramName), paramSource.getTypeName(paramName)));