Added missing class FileNameExtensionFilter

app/src/processing/app/javax/swing/filechooser/FileNameExtensionFilter.java

@@ -0,0 +1,48 @@
+package processing.app.javax.swing.filechooser;
+
+import javax.swing.filechooser.FileFilter;
+import java.io.File;
+import java.util.Locale;
+
+public class FileNameExtensionFilter extends FileFilter {
+
+  private final String description;
+  private final String[] extensions;
+
+  public FileNameExtensionFilter(String description, String... exts) {
+    this.description = description;
+    this.extensions = new String[exts.length];
+    for (int i = 0; i < exts.length; i++) {
+      this.extensions[i] = exts[i].toLowerCase(Locale.ENGLISH);
+    }
+  }
+
+  @Override
+  public boolean accept(File f) {
+    if (f == null) {
+      return false;
+    }
+
+    if (f.isDirectory()) {
+      return true;
+    }
+
+    String fileName = f.getName();
+    int i = fileName.lastIndexOf('.');
+    if (i > 0 && i < fileName.length() - 1) {
+      String fileExtension = fileName.substring(i + 1).toLowerCase(Locale.ENGLISH);
+      for (String extension : extensions) {
+        if (extension.equals(fileExtension)) {
+          return true;
+        }
+      }
+    }
+
+    return false;
+  }
+
+  @Override
+  public String getDescription() {
+    return description;
+  }
+}