org.apache.flink.util.StringUtils Maven / Gradle / Ivy
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* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.util;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.types.StringValue;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.io.IOException;
import java.util.Arrays;
import java.util.Random;
import static org.apache.flink.util.Preconditions.checkNotNull;
/**
* Utility class to convert objects into strings in vice-versa.
*/
@PublicEvolving
public final class StringUtils {
private static final char[] HEX_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
/**
* Given an array of bytes it will convert the bytes to a hex string
* representation of the bytes.
*
* @param bytes
* the bytes to convert in a hex string
* @param start
* start index, inclusively
* @param end
* end index, exclusively
* @return hex string representation of the byte array
*/
public static String byteToHexString(final byte[] bytes, final int start, final int end) {
if (bytes == null) {
throw new IllegalArgumentException("bytes == null");
}
int length = end - start;
char[] out = new char[length * 2];
for (int i = start, j = 0; i < end; i++) {
out[j++] = HEX_CHARS[(0xF0 & bytes[i]) >>> 4];
out[j++] = HEX_CHARS[0x0F & bytes[i]];
}
return new String(out);
}
/**
* Given an array of bytes it will convert the bytes to a hex string
* representation of the bytes.
*
* @param bytes
* the bytes to convert in a hex string
* @return hex string representation of the byte array
*/
public static String byteToHexString(final byte[] bytes) {
return byteToHexString(bytes, 0, bytes.length);
}
/**
* Given a hex string this will return the byte array corresponding to the
* string .
*
* @param hex
* the hex String array
* @return a byte array that is a hex string representation of the given
* string. The size of the byte array is therefore hex.length/2
*/
public static byte[] hexStringToByte(final String hex) {
final byte[] bts = new byte[hex.length() / 2];
for (int i = 0; i < bts.length; i++) {
bts[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
}
return bts;
}
/**
* This method calls {@link Object#toString()} on the given object, unless the
* object is an array. In that case, it will use the {@link #arrayToString(Object)}
* method to create a string representation of the array that includes all contained
* elements.
*
* @param o The object for which to create the string representation.
* @return The string representation of the object.
*/
public static String arrayAwareToString(Object o) {
if (o == null) {
return "null";
}
if (o.getClass().isArray()) {
return arrayToString(o);
}
return o.toString();
}
/**
* Returns a string representation of the given array. This method takes an Object
* to allow also all types of primitive type arrays.
*
* @param array The array to create a string representation for.
* @return The string representation of the array.
* @throws IllegalArgumentException If the given object is no array.
*/
public static String arrayToString(Object array) {
if (array == null) {
throw new NullPointerException();
}
if (array instanceof int[]) {
return Arrays.toString((int[]) array);
}
if (array instanceof long[]) {
return Arrays.toString((long[]) array);
}
if (array instanceof Object[]) {
return Arrays.toString((Object[]) array);
}
if (array instanceof byte[]) {
return Arrays.toString((byte[]) array);
}
if (array instanceof double[]) {
return Arrays.toString((double[]) array);
}
if (array instanceof float[]) {
return Arrays.toString((float[]) array);
}
if (array instanceof boolean[]) {
return Arrays.toString((boolean[]) array);
}
if (array instanceof char[]) {
return Arrays.toString((char[]) array);
}
if (array instanceof short[]) {
return Arrays.toString((short[]) array);
}
if (array.getClass().isArray()) {
return "";
} else {
throw new IllegalArgumentException("The given argument is no array.");
}
}
/**
* 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.
*
* @param str The string in which to replace the control characters.
* @return The string with the replaced characters.
*/
public static String showControlCharacters(String str) {
int len = str.length();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < len; i += 1) {
char c = str.charAt(i);
switch (c) {
case '\b':
sb.append("\\b");
break;
case '\t':
sb.append("\\t");
break;
case '\n':
sb.append("\\n");
break;
case '\f':
sb.append("\\f");
break;
case '\r':
sb.append("\\r");
break;
default:
sb.append(c);
}
}
return sb.toString();
}
/**
* 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.
*
* @param rnd The random used to create the strings.
* @param minLength The minimum string length.
* @param maxLength The maximum string length (inclusive).
* @return A random String.
*/
public static String getRandomString(Random rnd, int minLength, int maxLength) {
int len = rnd.nextInt(maxLength - minLength + 1) + minLength;
char[] data = new char[len];
for (int i = 0; i < data.length; i++) {
data[i] = (char) (rnd.nextInt(0x7fff) + 1);
}
return new String(data);
}
/**
* 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.
*
* @param rnd The random used to create the strings.
* @param minLength The minimum string length.
* @param maxLength The maximum string length (inclusive).
* @param minValue The minimum character value to occur.
* @param maxValue The maximum character value to occur.
* @return A random String.
*/
public static String getRandomString(Random rnd, int minLength, int maxLength, char minValue, char maxValue) {
int len = rnd.nextInt(maxLength - minLength + 1) + minLength;
char[] data = new char[len];
int diff = maxValue - minValue + 1;
for (int i = 0; i < data.length; i++) {
data[i] = (char) (rnd.nextInt(diff) + minValue);
}
return new String(data);
}
/**
* Writes a String to the given output.
* The written string can be read with {@link #readString(DataInputView)}.
*
* @param str The string to write
* @param out The output to write to
*
* @throws IOException Thrown, if the writing or the serialization fails.
*/
public static void writeString(@Nonnull String str, DataOutputView out) throws IOException {
checkNotNull(str);
StringValue.writeString(str, out);
}
/**
* Reads a non-null String from the given input.
*
* @param in The input to read from
* @return The deserialized String
*
* @throws IOException Thrown, if the reading or the deserialization fails.
*/
public static String readString(DataInputView in) throws IOException {
return StringValue.readString(in);
}
/**
* Writes a String to the given output. The string may be null.
* The written string can be read with {@link #readNullableString(DataInputView)}-
*
* @param str The string to write, or null.
* @param out The output to write to.
*
* @throws IOException Thrown, if the writing or the serialization fails.
*/
public static void writeNullableString(@Nullable String str, DataOutputView out) throws IOException {
if (str != null) {
out.writeBoolean(true);
writeString(str, out);
} else {
out.writeBoolean(false);
}
}
/**
* Reads a String from the given input. The string may be null and must have been written with
* {@link #writeNullableString(String, DataOutputView)}.
*
* @param in The input to read from.
* @return The deserialized string, or null.
*
* @throws IOException Thrown, if the reading or the deserialization fails.
*/
public static @Nullable String readNullableString(DataInputView in) throws IOException {
if (in.readBoolean()) {
return readString(in);
} else {
return null;
}
}
/**
* Checks if the string is null, empty, or contains only whitespace characters.
* A whitespace character is defined via {@link Character#isWhitespace(char)}.
*
* @param str The string to check
* @return True, if the string is null or blank, false otherwise.
*/
public static boolean isNullOrWhitespaceOnly(String str) {
if (str == null || str.length() == 0) {
return true;
}
final int len = str.length();
for (int i = 0; i < len; i++) {
if (!Character.isWhitespace(str.charAt(i))) {
return false;
}
}
return true;
}
/**
* 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.
*
* @param s1 The first string argument
* @param s2 The second string argument
*
* @return The concatenated string, or non-null argument, or null
*/
@Nullable
public static String concatenateWithAnd(@Nullable String s1, @Nullable String s2) {
if (s1 != null) {
return s2 == null ? s1 : s1 + " and " + s2;
}
else {
return s2;
}
}
// ------------------------------------------------------------------------
/** Prevent instantiation of this utility class. */
private StringUtils() {}
}
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