src/java.base/share/classes/java/lang/reflect/Executable.java

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this

@@ -24,13 +24,16 @@
  */
 
 package java.lang.reflect;
 
 import java.lang.annotation.*;
+import java.util.Arrays;
 import java.util.Map;
 import java.util.Objects;
 import java.util.StringJoiner;
+import java.util.stream.Stream;
+import java.util.stream.Collectors;
 
 import jdk.internal.misc.SharedSecrets;
 import sun.reflect.annotation.AnnotationParser;
 import sun.reflect.annotation.AnnotationSupport;
 import sun.reflect.annotation.TypeAnnotationParser;

@@ -107,23 +110,19 @@
             StringBuilder sb = new StringBuilder();
 
             printModifiersIfNonzero(sb, modifierMask, isDefault);
             specificToStringHeader(sb);
             sb.append('(');
-            StringJoiner sj = new StringJoiner(",");
-            for (Class<?> parameterType : parameterTypes) {
-                sj.add(parameterType.getTypeName());
-            }
-            sb.append(sj.toString());
+
+            sb.append(Stream.of(parameterTypes).map(p -> p.getTypeName()).
+                      collect(Collectors.joining(",")));
+
             sb.append(')');
 
             if (exceptionTypes.length > 0) {
-                StringJoiner joiner = new StringJoiner(",", " throws ", "");
-                for (Class<?> exceptionType : exceptionTypes) {
-                    joiner.add(exceptionType.getTypeName());
-                }
-                sb.append(joiner.toString());
+                sb.append(Stream.of(exceptionTypes).map(e -> e.getTypeName()).
+                          collect(Collectors.joining(",", " throws ", "")));
             }
             return sb.toString();
         } catch (Exception e) {
             return "<" + e + ">";
         }

@@ -133,23 +132,31 @@
      * Generate toString header information specific to a method or
      * constructor.
      */
     abstract void specificToStringHeader(StringBuilder sb);
 
+    String typeVarBounds(TypeVariable<?> typeVar) {
+        Type[] bounds = typeVar.getBounds();
+        if (bounds.length == 1 && bounds[0].equals(Object.class)) {
+            return typeVar.getName();
+        } else {
+            return typeVar.getName() + " extends " +
+                Stream.of(bounds).map(e -> e.getTypeName()).
+                collect(Collectors.joining(" & "));
+        }
+    }
+
     String sharedToGenericString(int modifierMask, boolean isDefault) {
         try {
             StringBuilder sb = new StringBuilder();
 
             printModifiersIfNonzero(sb, modifierMask, isDefault);
 
             TypeVariable<?>[] typeparms = getTypeParameters();
             if (typeparms.length > 0) {
-                StringJoiner sj = new StringJoiner(",", "<", "> ");
-                for(TypeVariable<?> typeparm: typeparms) {
-                    sj.add(typeparm.getTypeName());
-                }
-                sb.append(sj.toString());
+                sb.append(Stream.of(typeparms).map(t -> typeVarBounds(t)).
+                          collect(Collectors.joining(",", "<", "> ")));
             }
 
             specificToGenericStringHeader(sb);
 
             sb.append('(');