Change to use Stream API, Optional API and lambda expression If possible

Author: kazuki43zoo

src/main/java/org/apache/ibatis/builder/xml/XMLIncludeTransformer.java

@@ -17,6 +17,7 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 
 import org.apache.ibatis.builder.BuilderException;
@@ -45,9 +46,7 @@ public XMLIncludeTransformer(Configuration configuration, MapperBuilderAssistant
   public void applyIncludes(Node source) {
     Properties variablesContext = new Properties();
     Properties configurationVariables = configuration.getVariables();
-    if (configurationVariables != null) {
-      variablesContext.putAll(configurationVariables);
-    }
+    Optional.ofNullable(configurationVariables).ifPresent(variablesContext::putAll);
     applyIncludes(source, variablesContext, false);
   }
 

src/main/java/org/apache/ibatis/reflection/ParamNameUtil.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2018 the original author or authors.
+ *    Copyright 2009-2019 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -19,8 +19,9 @@
 import java.lang.reflect.Executable;
 import java.lang.reflect.Method;
 import java.lang.reflect.Parameter;
-import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Collectors;
 
 public class ParamNameUtil {
   public static List<String> getParamNames(Method method) {
@@ -32,12 +33,7 @@ public static List<String> getParamNames(Constructor<?> constructor) {
   }
 
   private static List<String> getParameterNames(Executable executable) {
-    final List<String> names = new ArrayList<>();
-    final Parameter[] params = executable.getParameters();
-    for (Parameter param : params) {
-      names.add(param.getName());
-    }
-    return names;
+    return Arrays.stream(executable.getParameters()).map(Parameter::getName).collect(Collectors.toList());
   }
 
   private ParamNameUtil() {

src/main/java/org/apache/ibatis/scripting/xmltags/DynamicSqlSource.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2017 the original author or authors.
+ *    Copyright 2009-2019 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -15,8 +15,6 @@
  */
 package org.apache.ibatis.scripting.xmltags;
 
-import java.util.Map;
-
 import org.apache.ibatis.builder.SqlSourceBuilder;
 import org.apache.ibatis.mapping.BoundSql;
 import org.apache.ibatis.mapping.SqlSource;
@@ -43,9 +41,7 @@ public BoundSql getBoundSql(Object parameterObject) {
     Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
     SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
     BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
-    for (Map.Entry<String, Object> entry : context.getBindings().entrySet()) {
-      boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
-    }
+    context.getBindings().forEach(boundSql::setAdditionalParameter);
     return boundSql;
   }
 

src/main/java/org/apache/ibatis/scripting/xmltags/MixedSqlNode.java

@@ -1,5 +1,5 @@
 /**
- *    Copyright 2009-2017 the original author or authors.
+ *    Copyright 2009-2019 the original author or authors.
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -29,9 +29,7 @@ public MixedSqlNode(List<SqlNode> contents) {
 
   @Override
   public boolean apply(DynamicContext context) {
-    for (SqlNode sqlNode : contents) {
-      sqlNode.apply(context);
-    }
+    contents.forEach(node -> node.apply(context));
     return true;
   }
 }