Java examples for java.lang:Math Calculation
Fast way to calculate the log2(x).
/*//from w w w.j a v a 2 s . c o m * 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. */ //package com.java2s; public class Main { /** * Fast way to calculate the log2(x). Note: x should be >= 1. * * @param n * @return */ public static int log2Floor(int n) { assert n >= 1; int log = 0; if (n > 0xffff) { n >>>= 16; log = 16; } if (n > 0xff) { n >>>= 8; log |= 8; } if (n > 0xf) { n >>>= 4; log |= 4; } if (n > 0b11) { n >>>= 2; log |= 2; } return log + (n >>> 1); } }