Remove dependency from {,More}Objects.ToStringHelper by copying code.

This is a copy of the pieces of MoreObjects.ToStringHelper necessary for the
more limited API exposed. No real implementation modifications were made, other
than deleting unused methods.

Objects.ToStringHelper is deprecated and is going to be removed. However, its
replacement MoreObjects.ToStringHelper is only available in Guava 18 which
won't receive a JDK5 backport. Copy the code for now to remove dependency.

Once the client library drops JDK5 support and swaps to Guava 18 it can swap to
using MoreObjects.ToStringHelper.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=107624331

Author: ejona86

google-http-client/src/main/java/com/google/api/client/util/Objects.java

@@ -17,10 +17,6 @@
 /**
  * Helper functions that can operate on any {@code Object}.
  *
- * <p>
- * NOTE: proxy for the Guava implementation of {@link com.google.common.base.Objects}.
- * </p>
- *
  * @since 1.14
  * @author Yaniv Inbar
  */
@@ -85,20 +81,22 @@ public static boolean equal(Object a, Object b) {
    *        class name
    */
   public static ToStringHelper toStringHelper(Object self) {
-    return new ToStringHelper(com.google.common.base.Objects.toStringHelper(self));
+    return new ToStringHelper(self.getClass().getSimpleName());
   }
 
+  // TODO(ejona): Swap to wrapping MoreObjects.ToStringHelper once depending on Guava 18.
   /** Support class for {@link Objects#toStringHelper}. */
   public static final class ToStringHelper {
-
-    /** Wrapped object. */
-    private final com.google.common.base.Objects.ToStringHelper wrapped;
+    private final String className;
+    private ValueHolder holderHead = new ValueHolder();
+    private ValueHolder holderTail = holderHead;
+    private boolean omitNullValues;
 
     /**
      * @param wrapped wrapped object
      */
-    ToStringHelper(com.google.common.base.Objects.ToStringHelper wrapped) {
-      this.wrapped = wrapped;
+    ToStringHelper(String className) {
+      this.className = className;
     }
 
     /**
@@ -107,7 +105,7 @@ public static final class ToStringHelper {
      * methods, is not significant.
      */
     public ToStringHelper omitNullValues() {
-      wrapped.omitNullValues();
+      omitNullValues = true;
       return this;
     }
 
@@ -117,13 +115,48 @@ public ToStringHelper omitNullValues() {
      * called, in which case this name/value pair will not be added.
      */
     public ToStringHelper add(String name, Object value) {
-      wrapped.add(name, value);
-      return this;
+      return addHolder(name, value);
     }
 
     @Override
     public String toString() {
-      return wrapped.toString();
+      // create a copy to keep it consistent in case value changes
+      boolean omitNullValuesSnapshot = omitNullValues;
+      String nextSeparator = "";
+      StringBuilder builder = new StringBuilder(32).append(className).append('{');
+      for (ValueHolder valueHolder = holderHead.next;
+          valueHolder != null;
+          valueHolder = valueHolder.next) {
+        if (!omitNullValuesSnapshot || valueHolder.value != null) {
+          builder.append(nextSeparator);
+          nextSeparator = ", ";
+
+          if (valueHolder.name != null) {
+            builder.append(valueHolder.name).append('=');
+          }
+          builder.append(valueHolder.value);
+        }
+      }
+      return builder.append('}').toString();
+    }
+
+    private ValueHolder addHolder() {
+      ValueHolder valueHolder = new ValueHolder();
+      holderTail = holderTail.next = valueHolder;
+      return valueHolder;
+    }
+
+    private ToStringHelper addHolder(String name, Object value) {
+      ValueHolder valueHolder = addHolder();
+      valueHolder.value = value;
+      valueHolder.name = Preconditions.checkNotNull(name);
+      return this;
+    }
+
+    private static final class ValueHolder {
+      String name;
+      Object value;
+      ValueHolder next;
     }
   }
 

google-http-client/src/test/java/com/google/api/client/util/ObjectsTest.java

@@ -22,18 +22,30 @@
  * @author Yaniv Inbar
  */
 public class ObjectsTest extends TestCase {
+  public void testToStringHelper() {
+    String toTest = Objects.toStringHelper(new TestClass()).add("hello", "world").toString();
+    assertEquals("TestClass{hello=world}", toTest);
+  }
 
-  class A {
-    String hello = "world";
+  public void testConstructor_innerClass() {
+    String toTest = Objects.toStringHelper(new TestClass()).toString();
+    assertEquals("TestClass{}", toTest);
+  }
 
-    @Override
-    public String toString() {
-      return Objects.toStringHelper(this).add("hello", hello).toString();
-    }
+  public void testToString_oneIntegerField() {
+    String toTest = Objects.toStringHelper(new TestClass())
+        .add("field1", new Integer(42))
+        .toString();
+    assertEquals("TestClass{field1=42}", toTest);
   }
 
-  public void testToStringHelper() {
-    A a = new A();
-    assertEquals("A{hello=world}", a.toString());
+  public void testToStringOmitNullValues_oneField() {
+    String toTest = Objects.toStringHelper(new TestClass())
+        .omitNullValues()
+        .add("field1", null)
+        .toString();
+    assertEquals("TestClass{}", toTest);
   }
+
+  private static class TestClass {}
 }