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src/main/java/gui/ValidationUtil.java

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+package gui;
+
+import java.io.File;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.lang3.math.NumberUtils;
+
+public class ValidationUtil {
+
+	public static boolean isNumber(String value) {
+		return NumberUtils.isCreatable(value);
+	}
+
+	/**
+	 * Checks if an object is empty or null. Null part is especially important,
+	 * since Java's built-in isEmpty() methods don't check for this condition
+	 * and throw a nullPointerException as a result.
+	 * <p>
+	 * Supported structures:
+	 * <ul>
+	 * <li>String: empty if null or length is zero</li>
+	 * <li>List: empty if null or size() == 0</li>
+	 * <li>Map: empty if null or if it contains no keys, or if all keys map to an empty value </li>
+	 * </ul>
+	 */
+	public static boolean isEmpty(Object o) {
+		if (o == null) {
+			return true;
+		}
+
+		if (o instanceof String) {
+			if (((String) o).length() == 0) {
+				return true;
+			}
+		}
+
+		if (o instanceof List) {
+			if (((List) o).isEmpty()) {
+				return true;
+			}
+		}
+
+		if (o instanceof Map) {
+			if (((Map) o).keySet().isEmpty()) {
+				return true;
+			} else {
+				for (Object val : ((Map) o).values()) {
+					if (!isEmpty(val)) {
+						// if map contains any value that isn't empty, the map isn't considered empty
+						return false;
+					}
+				}
+			}
+		}
+
+		return false;
+	}
+
+	public static boolean isNotEmpty(Object o) {
+		return !isEmpty(o);
+	}
+
+	/**
+	 * Checks whether a given File is a folder for which we have appropriate permission
+	 */
+	public static boolean isValidDirectory(File f) {
+		return f.isDirectory() && f.canRead() && f.canWrite();
+	}
+
+	/**
+	 * Checks whether a given File is a folder for which we have appropriate permission
+	 */
+	public static boolean isReadableDirectory(File f) {
+		return f.isDirectory() && f.canRead();
+	}
+}