Package org.apache.flink.util

Class StringUtils

java.lang.Object

org.apache.flink.util.StringUtils

@PublicEvolving
public final class StringUtils
extends Object

Utility class to convert objects into strings in vice-versa.

Field Summary

Fields

Modifier and Type	Field	Description
static String[]	EMPTY_STRING_ARRAY	An empty string array.

Method Summary

Modifier and Type	Method	Description
static String	arrayAwareToString(Object o)	Converts the given object into a string representation by calling Object.toString() and formatting (possibly nested) arrays and null.
static String	byteToHexString(byte[] bytes)	Given an array of bytes it will convert the bytes to a hex string representation of the bytes.
static String	byteToHexString(byte[] bytes, int start, int end)	Given an array of bytes it will convert the bytes to a hex string representation of the bytes.
static String	concatenateWithAnd(String s1, String s2)	If both string arguments are non-null, this method concatenates them with ' and '.
static String	generateRandomAlphanumericString(Random rnd, int length)	Creates a random alphanumeric string of given length.
static String	getRandomString(Random rnd, int minLength, int maxLength)	Creates a random string with a length within the given interval.
static String	getRandomString(Random rnd, int minLength, int maxLength, char minValue, char maxValue)	Creates a random string with a length within the given interval.
static byte[]	hexStringToByte(String hex)	Given a hex string this will return the byte array corresponding to the string .
static boolean	isNullOrWhitespaceOnly(String str)	Checks if the string is null, empty, or contains only whitespace characters.
static String	readNullableString(DataInputView in)	Reads a String from the given input.
static String	readString(DataInputView in)	Reads a non-null String from the given input.
static String	showControlCharacters(String str)	Replaces control characters by their escape-coded version.
static String	toQuotedListString(Object[] values)	Generates a string containing a comma-separated list of values in double-quotes.
static void	writeNullableString(String str, DataOutputView out)	Writes a String to the given output.
static void	writeString(String str, DataOutputView out)	Writes a String to the given output.

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_STRING_ARRAY

public static final String[] EMPTY_STRING_ARRAY

An empty string array. There are just too many places where one needs an empty string array and wants to save some object allocation.

Method Detail

byteToHexString

public static String byteToHexString(byte[] bytes,
                                     int start,
                                     int end)

Given an array of bytes it will convert the bytes to a hex string representation of the bytes.

Parameters:

bytes - the bytes to convert in a hex string

start - start index, inclusively

end - end index, exclusively

Returns:

hex string representation of the byte array

byteToHexString

public static String byteToHexString(byte[] bytes)

Given an array of bytes it will convert the bytes to a hex string representation of the bytes.

Parameters:

bytes - the bytes to convert in a hex string

Returns:

hex string representation of the byte array

hexStringToByte

public static byte[] hexStringToByte(String hex)

Given a hex string this will return the byte array corresponding to the string .

Parameters:

hex - the hex String array

Returns:

a byte array that is a hex string representation of the given string. The size of the byte array is therefore hex.length/2

arrayAwareToString

public static String arrayAwareToString(Object o)

Converts the given object into a string representation by calling Object.toString() and formatting (possibly nested) arrays and null.

See Arrays.deepToString(Object[]) for more information about the used format.

showControlCharacters

public static String showControlCharacters(String str)

Replaces control characters by their escape-coded version. For example, if the string contains a line break character ('\n'), this character will be replaced by the two characters backslash '\' and 'n'. As a consequence, the resulting string will not contain any more control characters.

Parameters:

str - The string in which to replace the control characters.

Returns:

The string with the replaced characters.

getRandomString

public static String getRandomString(Random rnd,
                                     int minLength,
                                     int maxLength)

Creates a random string with a length within the given interval. The string contains only characters that can be represented as a single code point.

Parameters:

rnd - The random used to create the strings.

minLength - The minimum string length.

maxLength - The maximum string length (inclusive).

Returns:

A random String.

getRandomString

public static String getRandomString(Random rnd,
                                     int minLength,
                                     int maxLength,
                                     char minValue,
                                     char maxValue)

Creates a random string with a length within the given interval. The string contains only characters that can be represented as a single code point.

Parameters:

rnd - The random used to create the strings.

minLength - The minimum string length.

maxLength - The maximum string length (inclusive).

minValue - The minimum character value to occur.

maxValue - The maximum character value to occur.

Returns:

A random String.

generateRandomAlphanumericString

public static String generateRandomAlphanumericString(Random rnd,
                                                      int length)

Creates a random alphanumeric string of given length.

Parameters:

rnd - The random number generator to use.

length - The number of alphanumeric characters to append.

writeString

public static void writeString(@Nonnull
                               String str,
                               DataOutputView out)
                        throws IOException

Writes a String to the given output. The written string can be read with readString(DataInputView).

Parameters:

str - The string to write

out - The output to write to

Throws:

IOException - Thrown, if the writing or the serialization fails.

readString

public static String readString(DataInputView in)
                         throws IOException

Reads a non-null String from the given input.

Parameters:

in - The input to read from

Returns:

The deserialized String

Throws:

IOException - Thrown, if the reading or the deserialization fails.

writeNullableString

public static void writeNullableString(@Nullable
                                       String str,
                                       DataOutputView out)
                                throws IOException

Writes a String to the given output. The string may be null. The written string can be read with readNullableString(DataInputView)-

Parameters:

str - The string to write, or null.

out - The output to write to.

Throws:

IOException - Thrown, if the writing or the serialization fails.

readNullableString

@Nullable
public static String readNullableString(DataInputView in)
                                 throws IOException

Reads a String from the given input. The string may be null and must have been written with writeNullableString(String, DataOutputView).

Parameters:

in - The input to read from.

Returns:

The deserialized string, or null.

Throws:

IOException - Thrown, if the reading or the deserialization fails.

isNullOrWhitespaceOnly

public static boolean isNullOrWhitespaceOnly(String str)

Checks if the string is null, empty, or contains only whitespace characters. A whitespace character is defined via Character.isWhitespace(char).

Parameters:

str - The string to check

Returns:

True, if the string is null or blank, false otherwise.

concatenateWithAnd

@Nullable
public static String concatenateWithAnd(@Nullable
                                        String s1,
                                        @Nullable
                                        String s2)

If both string arguments are non-null, this method concatenates them with ' and '. If only one of the arguments is non-null, this method returns the non-null argument. If both arguments are null, this method returns null.

Parameters:

s1 - The first string argument

s2 - The second string argument

Returns:

The concatenated string, or non-null argument, or null

toQuotedListString

public static String toQuotedListString(Object[] values)

Generates a string containing a comma-separated list of values in double-quotes. Uses lower-cased values returned from Object.toString() method for each element in the given array. Null values are skipped.

Parameters:

values - array of elements for the list

Returns:

The string with quoted list of elements