1 files changed, 10 insertions, 5 deletions

diff --git a/src/main/java/sevenUnits/utils/UncertainDouble.java b/src/main/java/sevenUnits/utils/UncertainDouble.java
index 8fe4b31..fe41104 100644
--- a/src/main/java/sevenUnits/utils/UncertainDouble.java
+++ b/src/main/java/sevenUnits/utils/UncertainDouble.java
@@ -36,13 +36,14 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 	 */
 	public static final UncertainDouble ZERO = UncertainDouble.of(0, 0);
 	
+	static final String NUMBER_REGEX = "(\\d+(?:[\\.,]\\d+))";
+	
 	/**
 	 * A regular expression that can recognize toString forms
 	 */
-	private static final Pattern TO_STRING = Pattern
-			.compile("([a-zA-Z_0-9\\.\\,]+)" // a number
-					// optional "± [number]"
-					+ "(?:\\s*(?:±|\\+-)\\s*([a-zA-Z_0-9\\.\\,]+))?");
+	static final Pattern TO_STRING = Pattern.compile(NUMBER_REGEX
+			// optional "± [number]"
+			+ "(?:\\s*(?:±|\\+-)\\s*" + NUMBER_REGEX + ")?");
 	
 	/**
 	 * Parses a string in the form of {@link UncertainDouble#toString(boolean)}
@@ -60,10 +61,14 @@ public final class UncertainDouble implements Comparable<UncertainDouble> {
 		Objects.requireNonNull(s, "s may not be null");
 		final Matcher matcher = TO_STRING.matcher(s);
 		
+		if (!matcher.matches())
+			throw new IllegalArgumentException(
+					"Could not parse stirng \"" + s + "\".");
+		
 		double value, uncertainty;
 		try {
 			value = Double.parseDouble(matcher.group(1));
-		} catch (IllegalStateException | NumberFormatException e) {
+		} catch (final NumberFormatException e) {
 			throw new IllegalArgumentException(
 					"String " + s + " not in correct format.");
 		}