Computes the logarithm of the given value to the base of 2, rounded down. - Java java.lang

Java examples for java.lang:Math Calculation

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Description

Computes the logarithm of the given value to the base of 2, rounded down.

Demo Code

/*//from   www  .  ja  va  2 s .  co 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,
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 * See the License for the specific language governing permissions and
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//package com.java2s;

public class Main {
    /**
     * Computes the logarithm of the given value to the base of 2, rounded down. It corresponds to the
     * position of the highest non-zero bit. The position is counted, starting with 0 from the least
     * significant bit to the most significant bit. For example, <code>log2floor(16) = 4</code>, and
     * <code>log2floor(10) = 3</code>.
     * 
     * @param value The value to compute the logarithm for.
     * @return The logarithm (rounded down) to the base of 2.
     * @throws ArithmeticException Thrown, if the given value is zero.
     */
    public static int log2floor(int value) throws ArithmeticException {
        if (value == 0) {
            throw new ArithmeticException("Logarithm of zero is undefined.");
        }

        return 31 - Integer.numberOfLeadingZeros(value);
    }
}

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