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feat: Added Map Reduce Design Pattern (#3184)

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* MapReduce design pattern added

* Updated README.md

* added module to parent pom
This commit is contained in:
Harshita Vidapanakal
2025-02-22 13:08:05 -05:00
committed by GitHub
parent e17f138223
commit 6785b53b02
14 changed files with 815 additions and 0 deletions
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map-reduce/src/main/java/com/iluwatar/Main.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;
/**
* The Main class serves as the entry point for executing the MapReduce program.
* It processes a list of text inputs, applies the MapReduce pattern, and prints the results.
*/
public class Main {
private static final Logger logger = Logger.getLogger(Main.class.getName());
/**
* The main method initiates the MapReduce process and displays the word count results.
*
* @param args Command-line arguments (not used).
*/
public static void main(String[] args) {
List<String> inputs = Arrays.asList(
"Hello world hello",
"MapReduce is fun",
"Hello from the other side",
"Hello world"
);
List<Map.Entry<String, Integer>> result = MapReduce.mapReduce(inputs);
for (Map.Entry<String, Integer> entry : result) {
logger.info(entry.getKey() + ": " + entry.getValue());
}
}
}
map-reduce/src/main/java/com/iluwatar/MapReduce.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* The MapReduce class orchestrates the MapReduce process,
* calling the Mapper, Shuffler, and Reducer components.
*/
public class MapReduce {
private MapReduce() {
throw new UnsupportedOperationException("MapReduce is a utility class and cannot be instantiated.");
}
/**
* Executes the MapReduce process on the given list of input strings.
*
* @param inputs List of input strings to be processed.
* @return A list of word counts sorted in descending order.
*/
public static List<Map.Entry<String, Integer>> mapReduce(List<String> inputs) {
List<Map<String, Integer>> mapped = new ArrayList<>();
for (String input : inputs) {
mapped.add(Mapper.map(input));
}
Map<String, List<Integer>> grouped = Shuffler.shuffleAndSort(mapped);
return Reducer.reduce(grouped);
}
}
map-reduce/src/main/java/com/iluwatar/Mapper.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar;
import java.util.HashMap;
import java.util.Map;
/**
* The Mapper class is responsible for processing an input string
* and generating a map of word occurrences.
*/
public class Mapper {
private Mapper() {
throw new UnsupportedOperationException("Mapper is a utility class and cannot be instantiated.");
}
/**
* Splits a given input string into words and counts their occurrences.
*
* @param input The input string to be mapped.
* @return A map where keys are words and values are their respective counts.
*/
public static Map<String, Integer> map(String input) {
Map<String, Integer> wordCount = new HashMap<>();
String[] words = input.split("\\s+");
for (String word : words) {
word = word.toLowerCase().replaceAll("[^a-z]", "");
if (!word.isEmpty()) {
wordCount.put(word, wordCount.getOrDefault(word, 0) + 1);
}
}
return wordCount;
}
}
map-reduce/src/main/java/com/iluwatar/Reducer.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* The Reducer class is responsible for aggregating word counts from the shuffled data.
*/
public class Reducer {
private Reducer() {
throw new UnsupportedOperationException("Reducer is a utility class and cannot be instantiated.");
}
/**
* Sums the occurrences of each word and sorts the results in descending order.
*
* @param grouped A map where keys are words and values are lists of their occurrences.
* @return A sorted list of word counts in descending order.
*/
public static List<Map.Entry<String, Integer>> reduce(Map<String, List<Integer>> grouped) {
Map<String, Integer> reduced = new HashMap<>();
for (Map.Entry<String, List<Integer>> entry : grouped.entrySet()) {
reduced.put(entry.getKey(), entry.getValue().stream().mapToInt(Integer::intValue).sum());
}
List<Map.Entry<String, Integer>> result = new ArrayList<>(reduced.entrySet());
result.sort(Map.Entry.comparingByValue(Comparator.reverseOrder()));
return result;
}
}
map-reduce/src/main/java/com/iluwatar/Shuffler.java
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/*
* This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
*
* The MIT License
* Copyright © 2014-2022 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* The Shuffler class is responsible for grouping word occurrences from multiple mappers.
*/
public class Shuffler {
private Shuffler() {
throw new UnsupportedOperationException("Shuffler is a utility class and cannot be instantiated.");
}
/**
* Merges multiple word count maps into a single grouped map.
*
* @param mapped List of maps containing word counts from the mapping phase.
* @return A map where keys are words and values are lists of their occurrences across inputs.
*/
public static Map<String, List<Integer>> shuffleAndSort(List<Map<String, Integer>> mapped) {
Map<String, List<Integer>> grouped = new HashMap<>();
for (Map<String, Integer> map : mapped) {
for (Map.Entry<String, Integer> entry : map.entrySet()) {
grouped.putIfAbsent(entry.getKey(), new ArrayList<>());
grouped.get(entry.getKey()).add(entry.getValue());
}
}
return grouped;
}
}