Create TopKWords.java

Others/TopKWords.java

@@ -0,0 +1,92 @@
+import  java.io.*;
+import  java.util.*;
+
+/* display the most frequent K words in the file and the times it appear 
+    in the file – shown in order (ignore case and periods) */
+
+public   class  TopKWords {
+    public static void main(String[] a) {
+        // you can replace the filePath with yours
+        CountWords cw = new CountWords("/Users/lisanaaa/Desktop/words.txt");
+        Map<String, Integer> dictionary = cw.getDictionary();  // get the words dictionary: {word: frequency}
+
+        // we change the map to list for convenient sort
+        List<Map.Entry<String, Integer>> list = new ArrayList<>(dictionary.entrySet());
+
+        // sort by lambda valueComparator
+        list.sort(Comparator.comparing(
+                m -> m.getValue())
+        );
+
+        Scanner input = new Scanner(System.in);
+        Integer k = new Integer(input.nextLine());
+        while (k > list.size()) {
+            System.out.println("Retype a number, your number is too large");
+            input = new Scanner(System.in);
+            k = new Integer(input.nextLine());
+        }
+        for (int i = 0; i<k; i++) {
+            System.out.println(list.get(list.size()-i-1));
+        }
+    }
+}
+
+class  CountWords {
+    private String fileName;
+
+    public CountWords(String fileName) {
+        this.fileName = fileName;
+    }
+
+    public Map<String, Integer> getDictionary() {
+        Map<String, Integer> dictionary = new HashMap<>();
+        FileInputStream fis = null;
+
+        try {
+
+            fis = new FileInputStream(fileName);  // open the file
+            int in = 0;
+            StringBuffer sb = new StringBuffer();  // load the word
+            in = fis.read();  // read one character
+            boolean notEnd = true;  // signal whether is the end of file
+
+            while (notEnd) {
+                // when in == -1 means get the end of the file
+                if (-1 == in) {
+                    notEnd = false;  //if false, end the while loop
+                }
+                if (Character.isLetter((char)in)) {
+                    sb.append((char)in);  //if get a letter, put it in StringBuffer
+                } else {
+                    // this branch means an entire word has just been read
+                    if (sb.length() > 0) {
+                        //see whether word exists in StringBuffer or not
+                        if (dictionary.containsKey(sb.toString())) {
+                            //if exist, count++
+                            dictionary.put(sb.toString(), dictionary.get(sb.toString()) + 1);
+                        } else {
+                            // if not exist, initiate count of this word with 1
+                            dictionary.put(sb.toString(), 1);
+                        }
+                    }
+                    sb = new StringBuffer(); //reload the StringBuffer
+                }
+                in = fis.read(); //read the character
+            }
+            return dictionary;
+        }
+        catch (IOException e) {
+            e.printStackTrace();
+        }
+        finally {
+            try {
+                // you always have to close the I/O streams
+                fis.close();
+            }
+            catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+        return null;
+    }
+}