GUACAMOLE-497: Remove usage of now-deprecated container class constructors.

guacamole-ext/src/main/java/org/apache/guacamole/form/NumericField.java

@@ -76,7 +76,7 @@ public class NumericField extends Field {
             return null;
 
         // Parse as integer
-        return new Integer(str);
+        return Integer.valueOf(str);
 
     }
 

guacamole-ext/src/main/java/org/apache/guacamole/properties/IntegerGuacamoleProperty.java

@@ -35,8 +35,7 @@ public abstract class IntegerGuacamoleProperty implements GuacamoleProperty<Inte
             return null;
 
         try {
-            Integer integer = new Integer(value);
-            return integer;
+            return Integer.valueOf(value);
         }
         catch (NumberFormatException e) {
             throw new GuacamoleServerException("Property \"" + getName() + "\" must be an integer.", e);

guacamole-ext/src/main/java/org/apache/guacamole/properties/LongGuacamoleProperty.java

@@ -35,8 +35,7 @@ public abstract class LongGuacamoleProperty implements GuacamoleProperty<Long> {
             return null;
 
         try {
-            Long longValue = new Long(value);
-            return longValue;
+            return Long.valueOf(value);
         }
         catch (NumberFormatException e) {
             throw new GuacamoleServerException("Property \"" + getName() + "\" must be an long.", e);