diff --git a/pattern-builder/src/main/java/org/panda/builder/Main.java b/pattern-builder/src/main/java/org/panda/builder/Main.java
index 5e0e170..8caa0c2 100644
--- a/pattern-builder/src/main/java/org/panda/builder/Main.java
+++ b/pattern-builder/src/main/java/org/panda/builder/Main.java
@@ -12,13 +12,13 @@ public class Main {
             usage();
             System.exit(0);
         }
-        if (args[0].equals("plain")){
+        if ("plain".equals(args[0])){
             TextBuilder textBuilder = new TextBuilder();
             Directory directory = new Directory(textBuilder);
             directory.construct();
             String result = textBuilder.getResult();
             System.out.println(result);
-        }else if (args[0].equals("html")){
+        }else if ("html".equals(args[0])){
             HTMLBuilder htmlBuilder = new HTMLBuilder();
             Directory directory = new Directory(htmlBuilder);
             directory.construct();;
diff --git a/pattern-interpreter/src/main/java/org/panda/interpreter/CommandListNode.java b/pattern-interpreter/src/main/java/org/panda/interpreter/CommandListNode.java
index 21157d3..4d3b76e 100644
--- a/pattern-interpreter/src/main/java/org/panda/interpreter/CommandListNode.java
+++ b/pattern-interpreter/src/main/java/org/panda/interpreter/CommandListNode.java
@@ -17,7 +17,7 @@ public class CommandListNode implements Node {
         while (true){
             if (context.currentToken() == null){
                 throw new ParseException("Missing 'end'");
-            }else if (context.currentToken().equals("end")){
+            }else if ("end".equals(context.currentToken())){
                 context.skipToken("end");
                 break;
             }else {
diff --git a/pattern-interpreter/src/main/java/org/panda/interpreter/PrimitiveCommandNode.java b/pattern-interpreter/src/main/java/org/panda/interpreter/PrimitiveCommandNode.java
index 236da7c..ec60611 100644
--- a/pattern-interpreter/src/main/java/org/panda/interpreter/PrimitiveCommandNode.java
+++ b/pattern-interpreter/src/main/java/org/panda/interpreter/PrimitiveCommandNode.java
@@ -12,7 +12,7 @@ public class PrimitiveCommandNode implements Node {
     public void parse(Context context) throws ParseException {
         name = context.currentToken();
         context.skipToken(name);
-        if (!name.equals("go")&&!name.equals("right")&&!name.equals("left")){
+        if (!"go".equals(name)&&!"right".equals(name)&&!"left".equals(name)){
             throw new ParseException(name+" is undefined");
         }
     }