diff --git a/src/scanner/LispScanner.java b/src/scanner/LispScanner.java
index 1908ec4..5501dfa 100644
--- a/src/scanner/LispScanner.java
+++ b/src/scanner/LispScanner.java
@@ -9,6 +9,7 @@ import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.text.MessageFormat;
+import java.util.function.Function;
 
 import constructs.Token;
 import constructs.TokenFactory;
@@ -34,26 +35,27 @@ public class LispScanner {
     }
 
     public Token getNextToken() throws IOException {
-        int c;
-
-        while ((c = inputStream.read()) != EOF) {
-            char nextChar = (char) c;
+        for (int c = inputStream.read(); c != EOF; c = inputStream.read()) {
+            char currentCharacter = (char) c;
             positionTracker.incrementColumn();
 
-            if (Character.isWhitespace(nextChar)) {
-                if (nextChar == NEWLINE)
+            if (Character.isWhitespace(currentCharacter)) {
+                if (currentCharacter == NEWLINE)
                     positionTracker.incrementLine();
-            } else {
-                FilePosition currentPosition = positionTracker.getCurrentPosition();
-                String tokenText = retrieveTokenText(nextChar);
-
-                return tokenFactory.createToken(tokenText, currentPosition);
-            }
+            } else
+                return createTokenFromCharacter(currentCharacter);
         }
 
         return tokenFactory.createEOFToken(positionTracker.getCurrentPosition());
     }
 
+    private Token createTokenFromCharacter(char c) throws IOException {
+        FilePosition currentPosition = positionTracker.getCurrentPosition();
+        String tokenText = retrieveTokenText(c);
+
+        return tokenFactory.createToken(tokenText, currentPosition);
+    }
+
     private String retrieveTokenText(char firstCharacter) throws IOException {
         String tokenText = "" + firstCharacter;
 
@@ -74,27 +76,16 @@ public class LispScanner {
 
         text.append(firstDoubleQuote);
 
-        int c;
-
-        while ((c = inputStream.read()) != EOF) {
+        for (int c = inputStream.read(); c != EOF; c = inputStream.read()) {
             char nextChar = (char) c;
 
             positionTracker.incrementColumn();
             text.append(nextChar);
 
-            switch (nextChar) {
-            case NEWLINE:
+            if (nextChar == NEWLINE)
                 positionTracker.incrementLine();
-                break;
-            case DOUBLE_QUOTE:
-                if (prevChar != BACKSLASH) {
-                    // we have found the terminating double quote
-
-                    return text.toString();
-                }
-
-                // this is an escaped double quote
-            }
+            else if ((nextChar == DOUBLE_QUOTE) && (prevChar != BACKSLASH))
+                return text.toString();
 
             prevChar = nextChar;
         }
@@ -103,55 +94,28 @@ public class LispScanner {
     }
 
     private String retrieveNumber(char firstDigit) throws IOException {
-        StringBuilder text = new StringBuilder();
-
-        text.append(firstDigit);
-        inputStream.mark(1);
-
-        int c;
-
-        while ((c = inputStream.read()) != EOF) {
-            char nextChar = (char) c;
-
-            if (Character.isDigit(nextChar)) {
-                // 'nextChar' is a digit in this number
-
-                text.append(nextChar);
-                positionTracker.incrementColumn();
-            } else {
-                // we have reached the end of the number
-
-                inputStream.reset(); // unread the last character
-
-                return text.toString();
-            }
-
-            inputStream.mark(1);
-        }
-
-        return text.toString();
+        return retrieveNumberOrIdentifier(firstDigit, Character::isDigit);
     }
 
-    private String retrieveIdentifier(char firstChar) throws IOException {
+    private String retrieveIdentifier(char firstCharacter) throws IOException {
+        return retrieveNumberOrIdentifier(firstCharacter, Characters::isLegalIdentifierCharacter);
+    }
+
+    private String retrieveNumberOrIdentifier(char firstCharacter, Function<Character, Boolean> isPartOfToken)
+            throws IOException {
         StringBuilder text = new StringBuilder();
 
-        text.append(firstChar);
+        text.append(firstCharacter);
         inputStream.mark(1);
 
-        int c;
-
-        while ((c = inputStream.read()) != EOF) {
+        for (int c = inputStream.read(); c != EOF; c = inputStream.read()) {
             char nextChar = (char) c;
 
-            if (Characters.isLegalIdentifierCharacter(nextChar)) {
-                // 'nextChar' is part of the identifier
-
+            if (isPartOfToken.apply(nextChar)) {
                 text.append(nextChar);
                 positionTracker.incrementColumn();
             } else {
-                // we have reached the end of this identifier
-
-                inputStream.reset(); // unread the last character
+                inputStream.reset();
 
                 return text.toString();
             }
diff --git a/src/util/Characters.java b/src/util/Characters.java
index 6e87a44..b6fac14 100644
--- a/src/util/Characters.java
+++ b/src/util/Characters.java
@@ -1,7 +1,7 @@
 package util;
 
-import java.util.HashMap;
-import java.util.Map;
+import java.util.HashSet;
+import java.util.Set;
 
 public class Characters {
 
@@ -19,25 +19,25 @@ public class Characters {
     public static final char SEMICOLON = ';';
     public static final char SINGLE_QUOTE = '\'';
     public static final char TICK_MARK = '`';
-    
-    public static final Map<Character, Boolean> illegalIdentifierCharacters = new HashMap<>();
+
+    public static final Set<Character> illegalIdentifierCharacters = new HashSet<>();
 
     static {
-        illegalIdentifierCharacters.put(DOUBLE_QUOTE, true);
-        illegalIdentifierCharacters.put(SINGLE_QUOTE, true);
-        illegalIdentifierCharacters.put(BACKSLASH, true);
-        illegalIdentifierCharacters.put(TICK_MARK, true);
-        illegalIdentifierCharacters.put(LEFT_PARENTHESIS, true);
-        illegalIdentifierCharacters.put(RIGHT_PARENTHESIS, true);
-        illegalIdentifierCharacters.put(LEFT_SQUARE_BRACKET, true);
-        illegalIdentifierCharacters.put(RIGHT_SQUARE_BRACKET, true);
-        illegalIdentifierCharacters.put(HASH, true);
-        illegalIdentifierCharacters.put(PERIOD, true);
-        illegalIdentifierCharacters.put(SEMICOLON, true);
+        illegalIdentifierCharacters.add(DOUBLE_QUOTE);
+        illegalIdentifierCharacters.add(SINGLE_QUOTE);
+        illegalIdentifierCharacters.add(BACKSLASH);
+        illegalIdentifierCharacters.add(TICK_MARK);
+        illegalIdentifierCharacters.add(LEFT_PARENTHESIS);
+        illegalIdentifierCharacters.add(RIGHT_PARENTHESIS);
+        illegalIdentifierCharacters.add(LEFT_SQUARE_BRACKET);
+        illegalIdentifierCharacters.add(RIGHT_SQUARE_BRACKET);
+        illegalIdentifierCharacters.add(HASH);
+        illegalIdentifierCharacters.add(PERIOD);
+        illegalIdentifierCharacters.add(SEMICOLON);
     }
-    
+
     public static boolean isLegalIdentifierCharacter(char c) {
-        return (! Character.isWhitespace(c)) && (! illegalIdentifierCharacters.containsKey(c));
+        return (!Character.isWhitespace(c)) && (!illegalIdentifierCharacters.contains(c));
     }
 
 }