Here you can find the source of bitsUsed(long value)
public static int bitsUsed(long value)
//package com.java2s; /*/*from w w w . j av a2 s .c om*/ * (c) Copyright 2007-2010 by Volker Bergmann. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, is permitted under the terms of the * GNU General Public License. * * For redistributing this software or a derivative work under a license other * than the GPL-compatible Free Software License as defined by the Free * Software Foundation or approved by OSI, you must first obtain a commercial * license to this software product from Volker Bergmann. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS, * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE * HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ public class Main { public static int bitsUsed(long value) { if (value < 0) return 64; for (int i = 62; i > 0; i--) if (((value >> i) & 1) == 1) return i + 1; return 1; } }