Several improvements

Signed-off-by: Rogiel <rogiel@rogiel.com>

src/main/java/com/l2jserver/util/calculator/SubtractFunction.java

@@ -0,0 +1,39 @@
+/*
+ * This file is part of l2jserver <l2jserver.com>.
+ *
+ * l2jserver is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * l2jserver is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with l2jserver.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.l2jserver.util.calculator;
+
+/**
+ * This function performs an subtraction: <blockquote><code>chain value -
+ * value</code></blockquote>
+ * 
+ * @author <a href="http://www.rogiel.com">Rogiel</a>
+ */
+public class SubtractFunction implements Function<Double> {
+	/**
+	 * The value
+	 */
+	private final double value;
+
+	public SubtractFunction(double value) {
+		this.value = value;
+	}
+
+	@Override
+	public Double calculate(Double value) {
+		return value - this.value;
+	}
+}