Java: Added access object for vector of struct and vector of tables. (#5233)

* Java: Added access object for vector of struct and vector of tables.

* Java: Workarounds removed when accessing the union vector.

java/com/google/flatbuffers/StringVector.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2019 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.flatbuffers;
+
+import static com.google.flatbuffers.Constants.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+
+/**
+ * Helper type for accessing vector of String.
+ */
+public final class StringVector extends BaseVector {
+  private Utf8 utf8 = Utf8.getDefault();
+
+  /**
+   * Assigns vector access object to vector data.
+   *
+   * @param _vector Start data of a vector.
+   * @param _element_size Size of a vector element.
+   * @param _bb Table's ByteBuffer.
+   * @return Returns current vector access object assigned to vector data whose offset is stored at
+   *         `vector`.
+   */
+  public StringVector __assign(int _vector, int _element_size, ByteBuffer _bb) {
+    __reset(_vector, _element_size, _bb); return this;
+  }
+
+  /**
+   * Reads the String at the given index.
+   *
+   * @param j The index from which the String value will be read.
+   * @return the String at the given index.
+   */
+  public String get(int j) {
+    return Table.__string(__element(j), bb, utf8);
+  }
+}