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Java example source code file (

This example Java source code file ( is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

exception, gson, interfacetest, obj_json, override, string, stringvalue, suppresswarnings, testcase, testobject, testobjectinterface, testobjectwrapper

The Java example source code

 * Copyright (C) 2008 Google Inc.
 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.



import junit.framework.TestCase;

 * Functional tests involving interfaces.
 * @author Inderjeet Singh
 * @author Joel Leitch
public class InterfaceTest extends TestCase {
  private static final String OBJ_JSON = "{\"someStringValue\":\"StringValue\"}";

  private Gson gson;
  private TestObject obj;

  protected void setUp() throws Exception {
    gson = new Gson();
    obj = new TestObject("StringValue");

  public void testSerializingObjectImplementingInterface() throws Exception {
    assertEquals(OBJ_JSON, gson.toJson(obj));
  public void testSerializingInterfaceObjectField() throws Exception {
    TestObjectWrapper objWrapper = new TestObjectWrapper(obj);
    assertEquals("{\"obj\":" + OBJ_JSON + "}", gson.toJson(objWrapper));

  private static interface TestObjectInterface {
    // Holder
  private static class TestObject implements TestObjectInterface {
    private String someStringValue;
    private TestObject(String value) {
      this.someStringValue = value;

  private static class TestObjectWrapper {
    private TestObjectInterface obj;
    private TestObjectWrapper(TestObjectInterface obj) {
      this.obj = obj;

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