Create readtext.md

Author: janbodnar

io/readtext.md

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+# Read text
+
+
+```
+The Battle of Thermopylae was fought between an alliance of
+Greek city-states, led by King Leonidas of Sparta, and the Persian Empire of
+Xerxes I over the course of three days, during the second Persian invasion of
+Greece. 
+```
+
+This is the `thermopylae.txt` file.  
+
+## FileReader with BufferedReader
+
+```java
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+void main() throws IOException {
+
+    var fileName = "thermopylae.txt";
+
+    try (var br = new BufferedReader(new FileReader(fileName,
+            StandardCharsets.UTF_8))) {
+
+        String line;
+        while ((line = br.readLine()) != null) {
+
+            System.out.println(line);
+        }
+    }
+}
+```
+
+## Word frequency
+
+```java
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.HashMap;
+import java.nio.charset.StandardCharsets;
+
+
+void main() throws IOException {
+
+    var fileName = "thermopylae.txt";
+    var wordFreq = new HashMap<String, Integer>();
+
+    try (var bufferedReader = new BufferedReader(new FileReader(fileName, 
+            StandardCharsets.UTF_8))) {
+
+        String line;
+        while ((line = bufferedReader.readLine()) != null) {
+
+            var words = line.split("\s");
+
+            for (var word : words) {
+
+                if (word.endsWith(",") || word.endsWith("?")
+                    || word.endsWith("!") || word.endsWith(".")) {
+
+                    word = word.substring(0, word.length()-1);
+                }
+
+                if (wordFreq.containsKey(word)) {
+                    wordFreq.put(word, wordFreq.get(word) + 1);
+                } else {
+                    wordFreq.put(word, 1);
+                }
+
+            }
+        }
+
+        wordFreq.forEach((k, v) -> {
+            System.out.printf("%s -> %d%n", k, v);
+        });
+    }
+}
+```
+