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Merge pull request #4 from wsw-stack/milestone4-haitong
Milestone4 haitong
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‎README-M4.md‎

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# Milestone 4 – Stream support for **JSONObject**
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## What is Added
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| Item | Description |
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|------|-------------|
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| `JSONObject.JSONNode` | Immutable leaf wrapper containing an absolute `path` and its `value`. |
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| `Stream<JSONNode> JSONObject.toStream()` | Depth-first, **lazy** flattening of any `JSONObject/JSONArray` into a `Stream`. Only leaf nodes are emitted (low memory footprint). |
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Path conventions
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* Object keys: `/parent/child`
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* Array items: `/array[0]/child`
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---
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## Run the test class
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```bash
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mvn -Dtest=org.json.junit.milestone4.tests.JSONObjectStreamTest test

‎src/main/java/org/json/JSONObject.java‎

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import java.util.*;
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import java.util.Map.Entry;
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import java.util.regex.Pattern;
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import java.util.stream.IntStream;
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import java.util.stream.Stream;
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/**
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* A JSONObject is an unordered collection of name/value pairs. Its external
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if (negativeFirstChar) {return "-0";}
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return "0";
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}
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// ---------------------------- Milestone 4 ------------------------------
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/**
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* Represents a node in the JSON object tree, with path and value.
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*/
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public static class JSONNode {
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private final String path;
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private final Object value;
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public JSONNode(String path, Object value) {
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this.path = path;
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this.value = value;
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}
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public String getPath() {
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return path;
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}
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public Object getValue() {
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return value;
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}
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@Override
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public String toString() {
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return "JSONNode{path='" + path + "', value=" + value + '}';
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}
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}
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/**
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* Convert this JSONObject into a stream of JSONNode, allowing chained operations.
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* @return Stream of JSONNode objects (each has a full path and a value)
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*/
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public Stream<JSONNode> toStream() {
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return toStream("", this);
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}
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/**
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* Recursive helper method to flatten JSONObject/JSONArray into JSONNode stream.
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*/
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private Stream<JSONNode> toStream(String path, Object value) {
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if (value instanceof JSONObject) {
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JSONObject obj = (JSONObject) value;
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return obj.keySet().stream()
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.flatMap(key -> {
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String newPath = path.isEmpty() ? "/" + key : path + "/" + key;
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return toStream(newPath, obj.get(key));
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});
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} else if (value instanceof JSONArray) {
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JSONArray array = (JSONArray) value;
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return IntStream.range(0, array.length())
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.boxed()
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.flatMap(i -> {
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String newPath = path + "[" + i + "]";
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return toStream(newPath, array.get(i));
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});
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} else {
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return Stream.of(new JSONNode(path, value));
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}
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}
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}

‎src/test/java/org/json/junit/milestone4/tests/JSONObjectStreamTest.java‎

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package org.json.junit.milestone4.tests;
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import org.json.JSONObject;
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import org.json.JSONObject.JSONNode;
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import org.json.XML;
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import org.junit.BeforeClass;
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import org.junit.Test;
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import java.io.InputStream;
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import java.nio.charset.StandardCharsets;
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import java.util.List;
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import java.util.Optional;
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import java.util.Scanner;
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import java.util.stream.Collectors;
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import static org.junit.Assert.*;
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/**
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* Unit tests for the JSONObject.toStream() extension (Milestone 4) – JUnit 4 / Java 8.
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*/
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public class JSONObjectStreamTest {
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private static JSONObject catalog;
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@BeforeClass
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public static void loadXml() throws Exception {
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try (InputStream in = JSONObjectStreamTest.class.getResourceAsStream("/books.xml")) {
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assertNotNull("books.xml must be on the class-path (src/test/resources)", in);
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String xml;
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try (Scanner scanner = new Scanner(in, StandardCharsets.UTF_8.name())) {
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scanner.useDelimiter("\\A");
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xml = scanner.hasNext() ? scanner.next() : "";
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}
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catalog = XML.toJSONObject(xml);
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}
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}
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@Test
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public void extractTitles() {
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List<String> titles = catalog.toStream()
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.filter(n -> n.getPath().endsWith("/title"))
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.map(n -> n.getValue().toString())
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.collect(Collectors.toList());
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assertEquals(12, titles.size());
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assertTrue(titles.contains("XML Developer's Guide"));
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assertTrue(titles.contains("Visual Studio 7: A Comprehensive Guide"));
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}
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@Test
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public void findExactPath() {
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String wantedPath = "/catalog/book[0]/author";
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Optional<JSONNode> node = catalog.toStream()
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.filter(n -> n.getPath().equals(wantedPath))
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.findFirst();
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assertTrue(node.isPresent());
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assertEquals("Gambardella, Matthew", node.get().getValue());
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}
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@Test
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public void filterCheapBooks() {
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List<JSONNode> cheapPrices = catalog.toStream()
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.filter(n -> n.getPath().endsWith("/price"))
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.filter(n -> Double.parseDouble(n.getValue().toString()) < 10.0)
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.collect(Collectors.toList());
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assertEquals(8, cheapPrices.size());
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assertTrue(cheapPrices.stream()
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.allMatch(n -> Double.parseDouble(n.getValue().toString()) < 10.0));
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}
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}

‎src/test/resources/books.xml‎

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<?xml version="1.0"?>
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<catalog>
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<book id="bk101">
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<author>Gambardella, Matthew</author>
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<title>XML Developer's Guide</title>
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<genre>Computer</genre>
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<price>44.95</price>
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<publish_date>2000-10-01</publish_date>
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<description>An in-depth look at creating applications
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with XML.</description>
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</book>
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<book id="bk102">
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<author>Ralls, Kim</author>
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<title>Midnight Rain</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2000-12-16</publish_date>
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<description>A former architect battles corporate zombies,
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an evil sorceress, and her own childhood to become queen
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of the world.</description>
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</book>
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<book id="bk103">
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<author>Corets, Eva</author>
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<title>Maeve Ascendant</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2000-11-17</publish_date>
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<description>After the collapse of a nanotechnology
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society in England, the young survivors lay the
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foundation for a new society.</description>
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</book>
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<book id="bk104">
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<author>Corets, Eva</author>
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<title>Oberon's Legacy</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2001-03-10</publish_date>
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<description>In post-apocalypse England, the mysterious
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agent known only as Oberon helps to create a new life
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for the inhabitants of London. Sequel to Maeve
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Ascendant.</description>
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</book>
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<book id="bk105">
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<author>Corets, Eva</author>
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<title>The Sundered Grail</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2001-09-10</publish_date>
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<description>The two daughters of Maeve, half-sisters,
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battle one another for control of England. Sequel to
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Oberon's Legacy.</description>
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</book>
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<book id="bk106">
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<author>Randall, Cynthia</author>
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<title>Lover Birds</title>
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<genre>Romance</genre>
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<price>4.95</price>
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<publish_date>2000-09-02</publish_date>
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<description>When Carla meets Paul at an ornithology
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conference, tempers fly as feathers get ruffled.</description>
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</book>
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<book id="bk107">
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<author>Thurman, Paula</author>
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<title>Splish Splash</title>
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<genre>Romance</genre>
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<price>4.95</price>
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<publish_date>2000-11-02</publish_date>
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<description>A deep sea diver finds true love twenty
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thousand leagues beneath the sea.</description>
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</book>
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<book id="bk108">
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<author>Knorr, Stefan</author>
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<title>Creepy Crawlies</title>
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<genre>Horror</genre>
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<price>4.95</price>
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<publish_date>2000-12-06</publish_date>
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<description>An anthology of horror stories about roaches,
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centipedes, scorpions and other insects.</description>
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</book>
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<book id="bk109">
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<author>Kress, Peter</author>
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<title>Paradox Lost</title>
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<genre>Science Fiction</genre>
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<price>6.95</price>
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<publish_date>2000-11-02</publish_date>
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<description>After an inadvertant trip through a Heisenberg
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Uncertainty Device, James Salway discovers the problems
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of being quantum.</description>
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</book>
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<book id="bk110">
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<author>O'Brien, Tim</author>
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<title>Microsoft .NET: The Programming Bible</title>
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<genre>Computer</genre>
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<price>36.95</price>
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<publish_date>2000-12-09</publish_date>
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<description>Microsoft's .NET initiative is explored in
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detail in this deep programmer's reference.</description>
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</book>
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<book id="bk111">
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<author>O'Brien, Tim</author>
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<title>MSXML3: A Comprehensive Guide</title>
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<genre>Computer</genre>
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<price>36.95</price>
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<publish_date>2000-12-01</publish_date>
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<description>The Microsoft MSXML3 parser is covered in
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detail, with attention to XML DOM interfaces, XSLT processing,
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SAX and more.</description>
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</book>
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<book id="bk112">
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<author>Galos, Mike</author>
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<title>Visual Studio 7: A Comprehensive Guide</title>
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<genre>Computer</genre>
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<price>49.95</price>
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<publish_date>2001-04-16</publish_date>
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<description>Microsoft Visual Studio 7 is explored in depth,
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looking at how Visual Basic, Visual C++, C#, and ASP+ are
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integrated into a comprehensive development
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environment.</description>
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</book>
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</catalog>

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