```
public final class Util
extends Object
```
All-purpose static-method container class.

Since:

0.1

Author:

Sebastiano Vigna

Field Summary

Fields
Modifier and Type Field Description

static Runtime RUNTIME
A static reference to Runtime.getRuntime().

Method Summary

Modifier and Type	Method	Description
`static long`	`availableMemory()`	Returns the amount of available memory (free memory plus never allocated memory).
`static void`	`compactMemory()`	Tries to compact memory as much as possible by forcing garbage collection.
`static String`	`format(double d)`	Formats a number.
`static String`	`format(double d, NumberFormat format)`	Formats a number using a specified `NumberFormat`.
`static String`	`format(long l)`	Formats a number.
`static String`	`format(long l, NumberFormat format)`	Formats a number using a specified `NumberFormat`.
`static String`	`formatBinarySize(long l)`	Formats a binary size.
`static String`	`formatBinarySize(long l, NumberFormat format)`	Formats a size using a specified `NumberFormat`.
`static String`	`formatSize(long l)`	Formats a size.
`static String`	`formatSize(long l, NumberFormat format)`	Formats a size using a specified `NumberFormat`.
`static String`	`formatSize2(long l)`	Formats a size.
`static String`	`formatSize2(long l, NumberFormat format)`	Formats a size using a specified `NumberFormat` and binary unit multipliers.
`static int[]`	`identity(int n)`	Stores the identity permutation in a new array of given length.
`static int[]`	`identity(int[] perm)`	Stores the identity permutation in an array.
`static long[][]`	`identity(long n)`	Stores the identity permutation in a new big array of given length.
`static long[][]`	`identity(long[][] perm)`	Stores the identity permutation in a big array.
`static int[]`	`invertPermutation(int[] perm)`	Computes the inverse of a permutation expressed as an array of `n` distinct integers in [0 .. `n`) and stores the result in a new array.
`static int[]`	`invertPermutation(int[] perm, int[] inv)`	Computes the inverse of a permutation expressed as an array of `n` distinct integers in [0 .. `n`).
`static long[][]`	`invertPermutation(long[][] perm)`	Computes the inverse of a permutation expressed as a big array of `n` distinct long integers in [0 .. `n`) and stores the result in a new big array.
`static long[][]`	`invertPermutation(long[][] perm, long[][] inv)`	Computes the inverse of a permutation expressed as a big array of `n` distinct long integers in [0 .. `n`).
`static int[]`	`invertPermutationInPlace(int[] perm)`	Computes in place the inverse of a permutation expressed as an array of `n` distinct integers in [0 .. `n`).
`static long[][]`	`invertPermutationInPlace(long[][] perm)`	Computes in place the inverse of a permutation expressed as a big array of `n` distinct long integers in [0 .. `n`).
`static boolean`	`memoryIsLow()`	Returns true if less then 5% of the available memory is free.
`static int`	`percAvailableMemory()`	Returns the percentage of available memory (free memory plus never allocated memory).
`static long`	`randomSeed()`	Returns a random seed generated by taking the output of a `XoRoShiRo128PlusRandomGenerator` (seeded at startup with `System.nanoTime()`) and xoring it with `System.nanoTime()`.
`static byte[]`	`randomSeedBytes()`	Returns a random seed generated by `randomSeed()` under the form of an array of eight bytes.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - RUNTIME
```
public static final Runtime RUNTIME
```
    A static reference to Runtime.getRuntime().
- Method Detail
  - format
```
public static String format(double d)
```
    Formats a number.
    This method formats a double separating thousands and printing just two fractional digits.
    Note that the method is synchronized, as it uses a static NumberFormat.
    
    Parameters:
    
    d - a number.
    
    Returns:
    
    a string containing a pretty print of the number.
  - format
```
public static String format(long l)
```
    Formats a number.
    This method formats a long separating thousands.
    Note that the method is synchronized, as it uses a static NumberFormat.
    
    Parameters:
    
    l - a number.
    
    Returns:
    
    a string containing a pretty print of the number.
  - format
```
public static String format(double d,
                            NumberFormat format)
```
    Formats a number using a specified NumberFormat.
    
    Parameters:
    
    d - a number.
    
    format - a format.
    
    Returns:
    
    a string containing a pretty print of the number.
  - format
```
public static String format(long l,
                            NumberFormat format)
```
    Formats a number using a specified NumberFormat.
    
    Parameters:
    
    l - a number.
    
    format - a format.
    
    Returns:
    
    a string containing a pretty print of the number.
  - formatSize
```
public static String formatSize(long l)
```
    Formats a size.
    This method formats a long using suitable unit multipliers (e.g., K, M, G, and T) and printing just two fractional digits.
    Note that the method is synchronized, as it uses a static NumberFormat.
    
    Parameters:
    
    l - a number, representing a size (e.g., memory).
    
    Returns:
    
    a string containing a pretty print of the number using unit multipliers.
  - formatBinarySize
```
public static String formatBinarySize(long l)
```
    Formats a binary size.
    This method formats a long using suitable unit binary multipliers (e.g., Ki, Mi, Gi, and Ti) and printing no fractional digits. The argument must be a power of 2.
    Note that the method is synchronized, as it uses a static NumberFormat.
    
    Parameters:
    
    l - a number, representing a binary size (e.g., memory); must be a power of 2.
    
    Returns:
    
    a string containing a pretty print of the number using binary unit multipliers.
  - formatSize2
```
public static String formatSize2(long l)
```
    Formats a size.
    This method formats a long using suitable binary unit multipliers (e.g., Ki, Mi, Gi, and Ti) and printing just two fractional digits.
    Note that the method is synchronized, as it uses a static NumberFormat.
    
    Parameters:
    
    l - a number, representing a size (e.g., memory).
    
    Returns:
    
    a string containing a pretty print of the number using binary unit multipliers.
  - formatSize
```
public static String formatSize(long l,
                                NumberFormat format)
```
    Formats a size using a specified NumberFormat.
    This method formats a long using suitable unit multipliers (e.g., K, M, G, and T) and the given NumberFormat for the digits.
    
    Parameters:
    
    l - a number, representing a size (e.g., memory).
    
    format - a format.
    
    Returns:
    
    a string containing a pretty print of the number using unit multipliers.
  - formatBinarySize
```
public static String formatBinarySize(long l,
                                      NumberFormat format)
```
    Formats a size using a specified NumberFormat.
    This method formats a long using suitable unit binary multipliers (e.g., Ki, Mi, Gi, and Ti) and the given NumberFormat for the digits. The argument must be a power of 2.
    
    Parameters:
    
    l - a number, representing a binary size (e.g., memory); must be a power of 2.
    
    format - a format.
    
    Returns:
    
    a string containing a pretty print of the number using binary unit multipliers.
  - formatSize2
```
public static String formatSize2(long l,
                                 NumberFormat format)
```
    Formats a size using a specified NumberFormat and binary unit multipliers.
    This method formats a long using suitable binary unit multipliers (e.g., Ki, Mi, Gi, and Ti) and the given NumberFormat for the digits.
    
    Parameters:
    
    l - a number, representing a size (e.g., memory).
    
    format - a format.
    
    Returns:
    
    a string containing a pretty print of the number using binary unit multipliers.
  - memoryIsLow
```
public static boolean memoryIsLow()
```
    Returns true if less then 5% of the available memory is free.
    
    Returns:
    
    true if less then 5% of the available memory is free.
  - availableMemory
```
public static long availableMemory()
```
    Returns the amount of available memory (free memory plus never allocated memory).
    
    Returns:
    
    the amount of available memory, in bytes.
  - percAvailableMemory
```
public static int percAvailableMemory()
```
    Returns the percentage of available memory (free memory plus never allocated memory).
    
    Returns:
    
    the percentage of available memory.
  - compactMemory
```
public static void compactMemory()
```
    Tries to compact memory as much as possible by forcing garbage collection.
  - randomSeed
```
public static long randomSeed()
```
    Returns a random seed generated by taking the output of a XoRoShiRo128PlusRandomGenerator (seeded at startup with System.nanoTime()) and xoring it with System.nanoTime().
    
    Returns:
    
    a reasonably good random seed.
  - randomSeedBytes
```
public static byte[] randomSeedBytes()
```
    Returns a random seed generated by randomSeed() under the form of an array of eight bytes.
    
    Returns:
    
    a reasonably good random seed.
  - invertPermutationInPlace
```
public static int[] invertPermutationInPlace(int[] perm)
```
    Computes in place the inverse of a permutation expressed as an array of n distinct integers in [0 .. n).
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    Returns:
    
    perm.
  - invertPermutation
```
public static int[] invertPermutation(int[] perm,
                                      int[] inv)
```
    Computes the inverse of a permutation expressed as an array of n distinct integers in [0 .. n).
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    inv - the array storing the inverse.
    
    Returns:
    
    inv.
  - invertPermutation
```
public static int[] invertPermutation(int[] perm)
```
    Computes the inverse of a permutation expressed as an array of n distinct integers in [0 .. n) and stores the result in a new array.
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    Returns:
    
    a new array containing the inverse permutation.
  - identity
```
public static int[] identity(int[] perm)
```
    Stores the identity permutation in an array.
    
    Parameters:
    
    perm - an array of integers.
    
    Returns:
    
    perm, filled with the identity permutation.
  - identity
```
public static int[] identity(int n)
```
    Stores the identity permutation in a new array of given length.
    
    Parameters:
    
    n - the size of the array.
    
    Returns:
    
    a new array of length n, filled with the identity permutation.
  - invertPermutationInPlace
```
public static long[][] invertPermutationInPlace(long[][] perm)
```
    Computes in place the inverse of a permutation expressed as a big array of n distinct long integers in [0 .. n).
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    Returns:
    
    perm.
  - invertPermutation
```
public static long[][] invertPermutation(long[][] perm,
                                         long[][] inv)
```
    Computes the inverse of a permutation expressed as a big array of n distinct long integers in [0 .. n).
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    inv - the big array storing the inverse.
    
    Returns:
    
    inv.
  - invertPermutation
```
public static long[][] invertPermutation(long[][] perm)
```
    Computes the inverse of a permutation expressed as a big array of n distinct long integers in [0 .. n) and stores the result in a new big array.
    Warning: if perm is not a permutation, essentially anything can happen.
    
    Parameters:
    
    perm - the permutation to be inverted.
    
    Returns:
    
    a new big array containing the inverse permutation.
  - identity
```
public static long[][] identity(long[][] perm)
```
    Stores the identity permutation in a big array.
    
    Parameters:
    
    perm - a big array.
    
    Returns:
    
    perm, filled with the identity permutation.
  - identity
```
public static long[][] identity(long n)
```
    Stores the identity permutation in a new big array of given length.
    
    Parameters:
    
    n - the size of the array.
    
    Returns:
    
    a new array of length n, filled with the identity permutation.

Class Util

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

RUNTIME

Method Detail

format

format

format

format

formatSize

formatBinarySize

formatSize2

formatSize

formatBinarySize

formatSize2

memoryIsLow

availableMemory

percAvailableMemory

compactMemory

randomSeed

randomSeedBytes

invertPermutationInPlace

invertPermutation

invertPermutation

identity

identity

invertPermutationInPlace

invertPermutation

invertPermutation

identity

identity