Get the smallest power of 2 > x. - Java java.lang

Java examples for java.lang:Math Calculation

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Description

Get the smallest power of 2 > x.

Demo Code

/*//from w w  w  . ja va 2 s.  c o m
 * Copyright (c) 2014. Real Time Genomics Limited.
 *
 * Use of this source code is bound by the Real Time Genomics Limited Software Licence Agreement
 * for Academic Non-commercial Research Purposes only.
 *
 * If you did not receive a license accompanying this file, a copy must first be obtained by email
 * from support@realtimegenomics.com.  On downloading, using and/or continuing to use this source
 * code you accept the terms of that license agreement and any amendments to those terms that may
 * be made from time to time by Real Time Genomics Limited.
 */
//package com.java2s;

public class Main {
    /**
     * Get the smallest power of 2 > x. Undefined for negative numbers or numbers
     * so large that there is no positive power of 2 available.
     *
     * @param x number being checked.
     * @return power of 2 > x.
     */
    public static int ceilPowerOf2Bits(final long x) {
        if (x >= (1L << 62) || x < 0) {
            throw new IllegalArgumentException("Number out of range:" + x);
        }
        long i = 1L;
        int n = 0;
        while (i <= x) {
            assert i > 0;
            assert n >= 0;
            n++;
            i = i << 1;
        }
        assert 1L << n == i;
        return n;
    }
}

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