Change to use the StringJoiner instead of the StringBuilder

Author: kazuki43zoo

src/main/java/org/apache/ibatis/builder/annotation/MapperAnnotationBuilder.java

@@ -348,15 +348,7 @@ void parseStatement(Method method) {
       String resultMapId = null;
       ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);
       if (resultMapAnnotation != null) {
-        String[] resultMaps = resultMapAnnotation.value();
-        StringBuilder sb = new StringBuilder();
-        for (String resultMap : resultMaps) {
-          if (sb.length() > 0) {
-            sb.append(",");
-          }
-          sb.append(resultMap);
-        }
-        resultMapId = sb.toString();
+        resultMapId = String.join(",", resultMapAnnotation.value());
       } else if (isSelect) {
         resultMapId = parseResultMap(method);
       }

src/main/java/org/apache/ibatis/cache/CacheKey.java

@@ -18,6 +18,7 @@
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.StringJoiner;
 
 import org.apache.ibatis.reflection.ArrayUtil;
 
@@ -112,10 +113,10 @@ public int hashCode() {
 
   @Override
   public String toString() {
-    StringBuilder returnValue = new StringBuilder().append(hashcode).append(':').append(checksum);
-    for (Object object : updateList) {
-      returnValue.append(':').append(ArrayUtil.toString(object));
-    }
+    StringJoiner returnValue = new StringJoiner(":");
+    returnValue.add(String.valueOf(hashcode));
+    returnValue.add(String.valueOf(checksum));
+    updateList.stream().map(ArrayUtil::toString).forEach(returnValue::add);
     return returnValue.toString();
   }
 

src/main/java/org/apache/ibatis/logging/jdbc/ResultSetLogger.java

@@ -24,6 +24,7 @@
 import java.sql.Types;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.StringJoiner;
 
 import org.apache.ibatis.logging.Log;
 import org.apache.ibatis.reflection.ExceptionUtil;
@@ -90,39 +91,28 @@ public Object invoke(Object proxy, Method method, Object[] params) throws Throwa
   }
 
   private void printColumnHeaders(ResultSetMetaData rsmd, int columnCount) throws SQLException {
-    StringBuilder row = new StringBuilder();
-    row.append("   Columns: ");
+    StringJoiner row = new StringJoiner(", ", "   Columns: ", "");
     for (int i = 1; i <= columnCount; i++) {
       if (BLOB_TYPES.contains(rsmd.getColumnType(i))) {
         blobColumns.add(i);
       }
-      String colname = rsmd.getColumnLabel(i);
-      row.append(colname);
-      if (i != columnCount) {
-        row.append(", ");
-      }
+      row.add(rsmd.getColumnLabel(i));
     }
     trace(row.toString(), false);
   }
 
   private void printColumnValues(int columnCount) {
-    StringBuilder row = new StringBuilder();
-    row.append("       Row: ");
+    StringJoiner row = new StringJoiner(", ", "       Row: ", "");
     for (int i = 1; i <= columnCount; i++) {
-      String colname;
       try {
         if (blobColumns.contains(i)) {
-          colname = "<<BLOB>>";
+          row.add("<<BLOB>>");
         } else {
-          colname = rs.getString(i);
+          row.add(rs.getString(i));
         }
       } catch (SQLException e) {
         // generally can't call getString() on a BLOB column
-        colname = "<<Cannot Display>>";
-      }
-      row.append(colname);
-      if (i != columnCount) {
-        row.append(", ");
+        row.add("<<Cannot Display>>");
       }
     }
     trace(row.toString(), false);

src/main/java/org/apache/ibatis/reflection/factory/DefaultObjectFactory.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.
@@ -19,14 +19,17 @@
 import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
+import java.util.stream.Collectors;
 
 import org.apache.ibatis.reflection.ReflectionException;
 import org.apache.ibatis.reflection.Reflector;
@@ -84,22 +87,10 @@ private  <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgType
         }
       }
     } catch (Exception e) {
-      StringBuilder argTypes = new StringBuilder();
-      if (constructorArgTypes != null && !constructorArgTypes.isEmpty()) {
-        for (Class<?> argType : constructorArgTypes) {
-          argTypes.append(argType.getSimpleName());
-          argTypes.append(",");
-        }
-        argTypes.deleteCharAt(argTypes.length() - 1); // remove trailing ,
-      }
-      StringBuilder argValues = new StringBuilder();
-      if (constructorArgs != null && !constructorArgs.isEmpty()) {
-        for (Object argValue : constructorArgs) {
-          argValues.append(String.valueOf(argValue));
-          argValues.append(",");
-        }
-        argValues.deleteCharAt(argValues.length() - 1); // remove trailing ,
-      }
+      String argTypes = Optional.ofNullable(constructorArgTypes).orElseGet(Collections::emptyList)
+          .stream().map(Class::getSimpleName).collect(Collectors.joining(","));
+      String argValues = Optional.ofNullable(constructorArgs).orElseGet(Collections::emptyList)
+          .stream().map(String::valueOf).collect(Collectors.joining(","));
       throw new ReflectionException("Error instantiating " + type + " with invalid types (" + argTypes + ") or values (" + argValues + "). Cause: " + e, e);
     }
   }

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

@@ -17,6 +17,7 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.StringJoiner;
 
 import ognl.OgnlContext;
 import ognl.OgnlRuntime;
@@ -38,7 +39,7 @@ public class DynamicContext {
   }
 
   private final ContextMap bindings;
-  private final StringBuilder sqlBuilder = new StringBuilder();
+  private final StringJoiner sqlBuilder = new StringJoiner(" ");
   private int uniqueNumber = 0;
 
   public DynamicContext(Configuration configuration, Object parameterObject) {
@@ -61,8 +62,7 @@ public void bind(String name, Object value) {
   }
 
   public void appendSql(String sql) {
-    sqlBuilder.append(sql);
-    sqlBuilder.append(" ");
+    sqlBuilder.add(sql);
   }
 
   public String getSql() {