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src/main/java/com/github/hcsp/multithread/WordCount.java

@@ -1,13 +1,61 @@
 package com.github.hcsp.multithread;
 
+import java.io.BufferedReader;
 import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 
 public class WordCount {
-    public WordCount(int threadNum) {}
+    private final int threadNum;
+    private ExecutorService threadPool;
+
+    public WordCount(int threadNum) {
+        threadPool = Executors.newFixedThreadPool(threadNum);
+        this.threadNum = threadNum;
+    }
 
     // 统计文件中各单词的数量
-    public Map<String, Integer> count(File file) {
-        return null;
+    public Map<String, Integer> count(File file) throws IOException, ExecutionException, InterruptedException {
+        BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
+        List<Future<Map<String, Integer>>> list = new ArrayList<>();
+        Map<String, Integer> finalResult = new HashMap<>();
+        for (int i = 0; i < threadNum; ++i) {
+            list.add(threadPool.submit(() -> {
+                Map<String, Integer> result = new HashMap<>();
+                String line;
+                while ((line = bufferedReader.readLine())!=null) {
+                    String[] oneThreadReadOneLine = line.split(" ");
+                    for (String element : oneThreadReadOneLine
+                    ) {
+                        result.put(element, result.getOrDefault(element, 0)+1);
+                    }
+                }
+                return result;
+            }));
+        }
+
+        for (Future<Map<String, Integer>> future : list
+        ) {
+            Map<String, Integer> resultFromThread = future.get();
+            mergeResultFromThread(resultFromThread, finalResult);
+        }
+        return finalResult;
+    }
+
+    private void mergeResultFromThread(Map<String, Integer> resultFromThread,
+                                       Map<String, Integer> finalResult) {
+        for (Map.Entry<String, Integer> entry : resultFromThread.entrySet()) {
+            int resultNumber = finalResult.getOrDefault(entry.getKey(), 0) + entry.getValue();
+            finalResult.put(entry.getKey(), resultNumber);
+        }
     }
 }
+