diff --git a/src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java b/src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java
index 72051b8b7e0..88532e1b92d 100644
--- a/src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java
+++ b/src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java
@@ -23,17 +23,8 @@
 import java.lang.reflect.Method;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
-import java.util.Optional;
-import java.util.Properties;
-import java.util.Set;
+import java.util.*;
+import java.util.stream.Collectors;
 
 import org.apache.ibatis.annotations.Arg;
 import org.apache.ibatis.annotations.CacheNamespace;
@@ -487,12 +478,9 @@ private SqlSource getSqlSourceFromAnnotations(Method method, Class<?> parameterT
   }
 
   private SqlSource buildSqlSourceFromStrings(String[] strings, Class<?> parameterTypeClass, LanguageDriver languageDriver) {
-    final StringBuilder sql = new StringBuilder();
-    for (String fragment : strings) {
-      sql.append(fragment);
-      sql.append(" ");
-    }
-    return languageDriver.createSqlSource(configuration, sql.toString().trim(), parameterTypeClass);
+    final String sql = Arrays.stream(strings).map(fragment -> fragment + " ").collect(Collectors.joining());
+
+    return languageDriver.createSqlSource(configuration, sql.trim(), parameterTypeClass);
   }
 
   private SqlCommandType getSqlCommandType(Method method) {
diff --git a/src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java b/src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java
index c944d713002..808a233121b 100644
--- a/src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java
+++ b/src/main/java/org/apache/ibatis/builder/xml/XMLMapperBuilder.java
@@ -25,6 +25,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.stream.Stream;
 
 import org.apache.ibatis.builder.BaseBuilder;
 import org.apache.ibatis.builder.BuilderException;
@@ -394,9 +395,7 @@ private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resu
   }
 
   private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings, Class<?> enclosingType) throws Exception {
-    if ("association".equals(context.getName())
-        || "collection".equals(context.getName())
-        || "case".equals(context.getName())) {
+    if (Stream.of("association", "collection", "case").anyMatch(s -> s.equals(context.getName()))) {
       if (context.getStringAttribute("select") == null) {
         validateCollection(context, enclosingType);
         ResultMap resultMap = resultMapElement(context, resultMappings, enclosingType);
diff --git a/src/main/java/org/apache/ibatis/io/JBoss6VFS.java b/src/main/java/org/apache/ibatis/io/JBoss6VFS.java
index a5856113be5..da6c40a0021 100644
--- a/src/main/java/org/apache/ibatis/io/JBoss6VFS.java
+++ b/src/main/java/org/apache/ibatis/io/JBoss6VFS.java
@@ -21,6 +21,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import org.apache.ibatis.logging.Log;
 import org.apache.ibatis.logging.LogFactory;
@@ -56,10 +57,9 @@ String getPathNameRelativeTo(VirtualFile parent) {
 
     List<VirtualFile> getChildren() throws IOException {
       List<?> objects = invoke(getChildrenRecursively, virtualFile);
-      List<VirtualFile> children = new ArrayList<>(objects.size());
-      for (Object object : objects) {
-        children.add(new VirtualFile(object));
-      }
+      List<VirtualFile> children = objects.stream()
+        .map(JBoss6VFS.VirtualFile::new)
+        .collect(Collectors.toCollection(() -> new ArrayList<>(objects.size())));
       return children;
     }
   }
diff --git a/src/main/java/org/apache/ibatis/type/ByteArrayUtils.java b/src/main/java/org/apache/ibatis/type/ByteArrayUtils.java
index 3067ce9de6f..636e6d0d5d5 100644
--- a/src/main/java/org/apache/ibatis/type/ByteArrayUtils.java
+++ b/src/main/java/org/apache/ibatis/type/ByteArrayUtils.java
@@ -15,6 +15,8 @@
  */
 package org.apache.ibatis.type;
 
+import java.util.stream.IntStream;
+
 /**
  * @author Clinton Begin
  */
@@ -33,10 +35,7 @@ static byte[] convertToPrimitiveArray(Byte[] objects) {
   }
 
   static Byte[] convertToObjectArray(byte[] bytes) {
-    final Byte[] objects = new Byte[bytes.length];
-    for (int i = 0; i < bytes.length; i++) {
-      objects[i] = bytes[i];
-    }
+    final Byte[] objects = IntStream.range(0, bytes.length).mapToObj(i -> bytes[i]).toArray(Byte[]::new);
     return objects;
   }
 }
diff --git a/src/test/java/org/apache/ibatis/domain/blog/ComplexImmutableAuthorId.java b/src/test/java/org/apache/ibatis/domain/blog/ComplexImmutableAuthorId.java
index 77832447100..496d343af4b 100644
--- a/src/test/java/org/apache/ibatis/domain/blog/ComplexImmutableAuthorId.java
+++ b/src/test/java/org/apache/ibatis/domain/blog/ComplexImmutableAuthorId.java
@@ -15,6 +15,8 @@
  */
 package org.apache.ibatis.domain.blog;
 
+import java.util.Objects;
+
 public class ComplexImmutableAuthorId {
   protected final int id;
   protected final String email;
@@ -58,13 +60,13 @@ public boolean equals(Object o) {
     if (id != that.id) {
       return false;
     }
-    if (email != null ? !email.equals(that.email) : that.email != null) {
+    if (!Objects.equals(email, that.email)) {
       return false;
     }
-    if (password != null ? !password.equals(that.password) : that.password != null) {
+    if (!Objects.equals(password, that.password)) {
       return false;
     }
-    if (username != null ? !username.equals(that.username) : that.username != null) {
+    if (!Objects.equals(username, that.username)) {
       return false;
     }