Java tutorial
import java.io.File; /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * */ public class Main { /** * For a double precision value x, this method returns +1.0 if x >= 0 and * -1.0 if x < 0. Returns <code>NaN</code> if <code>x</code> is * <code>NaN</code>. * * @param x the value, a double * @return +1.0 or -1.0, depending on the sign of x */ public static double indicator(final double x) { if (Double.isNaN(x)) { return Double.NaN; } return (x >= 0.0) ? 1.0 : -1.0; } }