net.cscott.jutil

Class Util

java.lang.Object

net.cscott.jutil.Util

public abstract class Util
extends Object

Miscellaneous static utility functions.

Version:

$Id: Util.java,v 1.2 2006-10-29 16:27:20 cananian Exp $

Author:

C. Scott Ananian

Constructor Summary

Constructors

Constructor and Description
Util()

Method Summary

Methods

Modifier and Type	Method and Description
static int	ffs(int v) Find first set (least significant bit).
static int	ffs(long v) Find first set (least significant bit).
static int	fls(int v) Find last set (most significant bit).
static int	fls(long v) Find last set (most significant bit).
static int	gcd(int u, int v) Returns the greatest common divisor of a pair of numbers.
static long	gcd(long u, long v) Returns the greatest common divisor of a pair of numbers.
static int	log2c(int v) Returns ceil(log2(n))
static int	popcount(int v) Return the number of ones in the binary representation of the value of the argument.
static int	popcount(long v) Return the number of ones in the binary representation of the value of the argument.
static String	repeatString(String s, int n) Repeat a given string a certain number of times.
static int	zerocount(int v) Return the number of zeros in the binary representation of the value of the argument.
static int	zerocount(long v) Return the number of zeros in the binary representation of the value of the argument.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Util

public Util()

Method Detail

repeatString

public static final String repeatString(String s,
                  int n)

Repeat a given string a certain number of times.

Returns:

a string consisting of s repeated n times.

ffs

public static final int ffs(int v)

Find first set (least significant bit).

Returns:

the first bit set in the argument. ffs(0)==0 and ffs(1)==1.

ffs

public static final int ffs(long v)

Find first set (least significant bit).

Returns:

the first bit set in the argument. ffs(0)==0 and ffs(1)==1.

fls

public static final int fls(int v)

Find last set (most significant bit).

Returns:

the last bit set in the argument. fls(0)==0 and fls(1)==1.

fls

public static final int fls(long v)

Find last set (most significant bit).

Returns:

the last bit set in the argument. fls(0)==0 and fls(1)==1.

log2c

public static final int log2c(int v)

Returns ceil(log2(n))

zerocount

public static final int zerocount(int v)

Return the number of zeros in the binary representation of the value of the argument.

zerocount

public static final int zerocount(long v)

Return the number of zeros in the binary representation of the value of the argument.

popcount

public static final int popcount(int v)

Return the number of ones in the binary representation of the value of the argument.

popcount

public static final int popcount(long v)

Return the number of ones in the binary representation of the value of the argument.

gcd

public static final long gcd(long u,
       long v)

Returns the greatest common divisor of a pair of numbers.

gcd

public static final int gcd(int u,
      int v)

Returns the greatest common divisor of a pair of numbers.