Add boolean parsed Text

dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/impl/BooleanBoundary.java

@@ -8,9 +8,6 @@ import de.unikoblenz.fgbks.base.utils.boundary.BoundaryParseException;
 
 public class BooleanBoundary extends AbstractGrowingBoundary<Boolean> {
 
-  private static final String TRUE_STRING = "true";
-  private static final String FALSE_STRING = "false";
-
   public BooleanBoundary(String text) {
     super(text, Boolean.TYPE);
   }
@@ -48,12 +45,17 @@ public class BooleanBoundary extends AbstractGrowingBoundary<Boolean> {
     if (text.trim().isEmpty()) {
       lowerBound = getMinValue();
       upperBound = getMaxValue();
-    } else if (TRUE_STRING.equals(text.toLowerCase())) {
+    } else if (Boolean.TRUE.toString().equals(text.toLowerCase())) {
       lowerBound = upperBound = getMaxValue();
-    } else if (FALSE_STRING.equals(text.toLowerCase())) {
+    } else if (Boolean.FALSE.toString().equals(text.toLowerCase())) {
       lowerBound = upperBound = getMinValue();
     } else {
       throw new BoundaryParseException("Boolean value cloud not be parsed: " + text);
     }
   }
+
+  @Override
+  public String getParsedText() {
+    return lowerBound != upperBound ? "" : lowerBound.toString();
+  }
 }