diff --git a/src/main/java/ninja/javafx/smartcsv/export/ErrorExport.java b/src/main/java/ninja/javafx/smartcsv/export/ErrorExport.java
index 2732d29..d99ee76 100644
--- a/src/main/java/ninja/javafx/smartcsv/export/ErrorExport.java
+++ b/src/main/java/ninja/javafx/smartcsv/export/ErrorExport.java
@@ -29,7 +29,6 @@ package ninja.javafx.smartcsv.export;
 import javafx.concurrent.Service;
 import javafx.concurrent.Task;
 import ninja.javafx.smartcsv.fx.table.model.CSVModel;
-import ninja.javafx.smartcsv.validation.ValidationError;
 
 import java.io.File;
 import java.io.StringWriter;
diff --git a/src/main/java/ninja/javafx/smartcsv/fx/table/EditableValidationCell.java b/src/main/java/ninja/javafx/smartcsv/fx/table/EditableValidationCell.java
index 270dabe..8617928 100644
--- a/src/main/java/ninja/javafx/smartcsv/fx/table/EditableValidationCell.java
+++ b/src/main/java/ninja/javafx/smartcsv/fx/table/EditableValidationCell.java
@@ -125,7 +125,7 @@ public class EditableValidationCell extends TableCell<CSVRow, CSVValue> {
         });
     }
 
-    private class ValueTextField extends TextField {
+    private static class ValueTextField extends TextField {
         private CSVValue value;
 
         public ValueTextField(CSVValue value) {
diff --git a/src/main/java/ninja/javafx/smartcsv/fx/table/ObservableMapValueFactory.java b/src/main/java/ninja/javafx/smartcsv/fx/table/ObservableMapValueFactory.java
index c72ec9a..893cd1c 100644
--- a/src/main/java/ninja/javafx/smartcsv/fx/table/ObservableMapValueFactory.java
+++ b/src/main/java/ninja/javafx/smartcsv/fx/table/ObservableMapValueFactory.java
@@ -47,7 +47,6 @@ public class ObservableMapValueFactory implements
     @Override
     public ObjectProperty<CSVValue> call(TableColumn.CellDataFeatures<CSVRow, CSVValue> features) {
         CSVRow row = features.getValue();
-        ObjectProperty<CSVValue> value = row.getColumns().get(key);
-        return value;
+        return row.getColumns().get(key);
     }
 }
diff --git a/src/main/java/ninja/javafx/smartcsv/preferences/PreferencesFileReader.java b/src/main/java/ninja/javafx/smartcsv/preferences/PreferencesFileReader.java
index a8170b9..5414ed2 100644
--- a/src/main/java/ninja/javafx/smartcsv/preferences/PreferencesFileReader.java
+++ b/src/main/java/ninja/javafx/smartcsv/preferences/PreferencesFileReader.java
@@ -43,7 +43,6 @@ import static ninja.javafx.smartcsv.preferences.QuoteModeHelper.getQuoteMode;
  */
 public class PreferencesFileReader implements FileReader<CsvPreference> {
 
-    private Map config;
     private CsvPreference csvPreference;
 
     public PreferencesFileReader() {
@@ -54,14 +53,14 @@ public class PreferencesFileReader implements FileReader<CsvPreference> {
 
     @Override
     public void read(File filename) throws IOException {
-        config = new GsonBuilder().create().fromJson(new java.io.FileReader(filename), HashMap.class);
+        Map config = new GsonBuilder().create().fromJson(new java.io.FileReader(filename), HashMap.class);
 
         if (config != null) {
             char quoteChar = config.get("quoteChar").toString().charAt(0);
             char delimiterChar = config.get("delimiterChar").toString().charAt(0);
             String endOfLineSymbols = config.get("endOfLineSymbols").toString();
-            boolean surroundingSpacesNeedQuotes = (Boolean)config.get("surroundingSpacesNeedQuotes");
-            boolean ignoreEmptyLines = (Boolean)config.get("ignoreEmptyLines");
+            boolean surroundingSpacesNeedQuotes = (Boolean) config.get("surroundingSpacesNeedQuotes");
+            boolean ignoreEmptyLines = (Boolean) config.get("ignoreEmptyLines");
             String quoteMode = config.get("quoteMode").toString();
 
             csvPreference = new CsvPreference.Builder(quoteChar, delimiterChar, endOfLineSymbols)
diff --git a/src/main/java/ninja/javafx/smartcsv/validation/checker/GroovyValidation.java b/src/main/java/ninja/javafx/smartcsv/validation/checker/GroovyValidation.java
index 2872d21..4e2fbbe 100644
--- a/src/main/java/ninja/javafx/smartcsv/validation/checker/GroovyValidation.java
+++ b/src/main/java/ninja/javafx/smartcsv/validation/checker/GroovyValidation.java
@@ -37,11 +37,11 @@ import org.codehaus.groovy.control.CompilationFailedException;
 public class GroovyValidation extends EmptyValueIsValid {
 
     private String groovyScript;
-    private GroovyShell shell = new GroovyShell();
     private Script script;
 
     public GroovyValidation(String groovyScript) {
         this.groovyScript = groovyScript;
+        GroovyShell shell = new GroovyShell();
         script = shell.parse(groovyScript);
     }
 
diff --git a/src/main/java/ninja/javafx/smartcsv/validation/checker/UuidValidation.java b/src/main/java/ninja/javafx/smartcsv/validation/checker/UuidValidation.java
index 0838072..ccf2cbc 100644
--- a/src/main/java/ninja/javafx/smartcsv/validation/checker/UuidValidation.java
+++ b/src/main/java/ninja/javafx/smartcsv/validation/checker/UuidValidation.java
@@ -34,6 +34,7 @@ import java.util.UUID;
  */
 public class UuidValidation extends EmptyValueIsValid {
 
+    @SuppressWarnings("ResultOfMethodCallIgnored")
     @Override
     public void check(int row, String value, ValidationError error) {
         try {
diff --git a/src/test/java/ninja/javafx/smartcsv/preferences/CharsetHelperTest.java b/src/test/java/ninja/javafx/smartcsv/preferences/CharsetHelperTest.java
index 422290a..8c5ec5a 100644
--- a/src/test/java/ninja/javafx/smartcsv/preferences/CharsetHelperTest.java
+++ b/src/test/java/ninja/javafx/smartcsv/preferences/CharsetHelperTest.java
@@ -28,7 +28,6 @@ package ninja.javafx.smartcsv.preferences;
 
 import org.junit.jupiter.api.Test;
 
-import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 
 import static org.junit.jupiter.api.Assertions.*;
diff --git a/src/test/java/ninja/javafx/smartcsv/validation/HeaderValidationTest.java b/src/test/java/ninja/javafx/smartcsv/validation/HeaderValidationTest.java
index 987ce20..5f29229 100644
--- a/src/test/java/ninja/javafx/smartcsv/validation/HeaderValidationTest.java
+++ b/src/test/java/ninja/javafx/smartcsv/validation/HeaderValidationTest.java
@@ -39,7 +39,6 @@ import java.util.List;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
-import static java.util.stream.Collectors.joining;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
@@ -115,6 +114,7 @@ public class HeaderValidationTest {
         });
     }
 
+    @SuppressWarnings("StringConcatenationInLoop")
     public static String json(String... headerNames) {
 
         String json = "{ \"fields\": [";