org.apache.logging.log4j.util.Strings Maven / Gradle / Ivy
/*
* 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.logging.log4j.util;
import static org.apache.logging.log4j.util.StringBuilders.trimToMaxSize;
import java.util.Iterator;
import java.util.Locale;
import java.util.Objects;
/**
* Consider this class private.
*
* @see Apache Commons Lang
*/
@InternalApi
public final class Strings {
// 518 allows the `StringBuilder` to resize three times from its initial size.
// This should be sufficient for most use cases.
private static final int MAX_FORMAT_BUFFER_LENGTH = 518;
private static final ThreadLocal FORMAT_BUFFER_REF = ThreadLocal.withInitial(StringBuilder::new);
/**
* The empty string.
*/
public static final String EMPTY = "";
private static final String COMMA_DELIMITED_RE = "\\s*,\\s*";
/**
* The empty array.
*/
public static final String[] EMPTY_ARRAY = {};
/**
* OS-dependent line separator, defaults to {@code "\n"} if the system property {@code ""line.separator"} cannot be
* read.
*/
public static final String LINE_SEPARATOR =
SystemPropertiesPropertySource.getSystemProperty("line.separator", "\n");
/**
* Returns a double quoted string.
*
* @param str a String
* @return {@code "str"}
*/
public static String dquote(final String str) {
return Chars.DQUOTE + str + Chars.DQUOTE;
}
/**
* Checks if a String is blank. A blank string is one that is either
* {@code null}, empty, or all characters are {@link Character#isWhitespace(char)}.
*
* @param s the String to check, may be {@code null}
* @return {@code true} if the String is {@code null}, empty, or all characters are {@link Character#isWhitespace(char)}
*/
public static boolean isBlank(final String s) {
if (s == null || s.isEmpty()) {
return true;
}
for (int i = 0; i < s.length(); i++) {
final char c = s.charAt(i);
if (!Character.isWhitespace(c)) {
return false;
}
}
return true;
}
/**
*
* Checks if a CharSequence is empty ("") or null.
*
*
*
* Strings.isEmpty(null) = true
* Strings.isEmpty("") = true
* Strings.isEmpty(" ") = false
* Strings.isEmpty("bob") = false
* Strings.isEmpty(" bob ") = false
*
*
*
* NOTE: This method changed in Lang version 2.0. It no longer trims the CharSequence. That functionality is
* available in isBlank().
*
*
*
* Copied from Apache Commons Lang org.apache.commons.lang3.StringUtils.isEmpty(CharSequence)
*
*
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is empty or null
*/
public static boolean isEmpty(final CharSequence cs) {
return cs == null || cs.length() == 0;
}
/**
* Checks if a String is not blank. The opposite of {@link #isBlank(String)}.
*
* @param s the String to check, may be {@code null}
* @return {@code true} if the String is non-{@code null} and has content after being trimmed.
*/
public static boolean isNotBlank(final String s) {
return !isBlank(s);
}
/**
*
* Checks if a CharSequence is not empty ("") and not null.
*
*
*
* Strings.isNotEmpty(null) = false
* Strings.isNotEmpty("") = false
* Strings.isNotEmpty(" ") = true
* Strings.isNotEmpty("bob") = true
* Strings.isNotEmpty(" bob ") = true
*
*
*
* Copied from Apache Commons Lang org.apache.commons.lang3.StringUtils.isNotEmpty(CharSequence)
*
*
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is not empty and not null
*/
public static boolean isNotEmpty(final CharSequence cs) {
return !isEmpty(cs);
}
/**
* Joins the elements of the provided {@code Iterable} into
* a single String containing the provided elements.
*
* No delimiter is added before or after the list. Null objects or empty
* strings within the iteration are represented by empty strings.
*
* @param iterable the {@code Iterable} providing the values to join together, may be null
* @param separator the separator character to use
* @return the joined String, {@code null} if null iterator input
*/
public static String join(final Iterable iterable, final char separator) {
if (iterable == null) {
return null;
}
return join(iterable.iterator(), separator);
}
/**
* Joins the elements of the provided {@code Iterator} into
* a single String containing the provided elements.
*
* No delimiter is added before or after the list. Null objects or empty
* strings within the iteration are represented by empty strings.
*
* @param iterator the {@code Iterator} of values to join together, may be null
* @param separator the separator character to use
* @return the joined String, {@code null} if null iterator input
*/
public static String join(final Iterator iterator, final char separator) {
// handle null, zero and one elements before building a buffer
if (iterator == null) {
return null;
}
if (!iterator.hasNext()) {
return EMPTY;
}
final Object first = iterator.next();
if (!iterator.hasNext()) {
return Objects.toString(first, EMPTY);
}
// two or more elements
final StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small
if (first != null) {
buf.append(first);
}
while (iterator.hasNext()) {
buf.append(separator);
final Object obj = iterator.next();
if (obj != null) {
buf.append(obj);
}
}
return buf.toString();
}
public static String[] splitList(final String string) {
return string != null ? string.split(COMMA_DELIMITED_RE) : new String[0];
}
/**
* Gets the leftmost {@code len} characters of a String.
*
* If {@code len} characters are not available, or the
* String is {@code null}, the String will be returned without
* an exception. An empty String is returned if len is negative.
*
*
* StringUtils.left(null, *) = null
* StringUtils.left(*, -ve) = ""
* StringUtils.left("", *) = ""
* StringUtils.left("abc", 0) = ""
* StringUtils.left("abc", 2) = "ab"
* StringUtils.left("abc", 4) = "abc"
*
*
*
* Copied from Apache Commons Lang org.apache.commons.lang3.StringUtils.
*
*
* @param str the String to get the leftmost characters from, may be null
* @param len the length of the required String
* @return the leftmost characters, {@code null} if null String input
*/
public static String left(final String str, final int len) {
if (str == null) {
return null;
}
if (len < 0) {
return EMPTY;
}
if (str.length() <= len) {
return str;
}
return str.substring(0, len);
}
/**
* Returns a quoted string.
*
* @param str a String
* @return {@code 'str'}
*/
public static String quote(final String str) {
return Chars.QUOTE + str + Chars.QUOTE;
}
/**
*
* Removes control characters (char <= 32) from both ends of this String returning {@code null} if the String is
* empty ("") after the trim or if it is {@code null}.
*
*
* The String is trimmed using {@link String#trim()}. Trim removes start and end characters <= 32.
*
*
*
* Strings.trimToNull(null) = null
* Strings.trimToNull("") = null
* Strings.trimToNull(" ") = null
* Strings.trimToNull("abc") = "abc"
* Strings.trimToNull(" abc ") = "abc"
*
*
*
* Copied from Apache Commons Lang org.apache.commons.lang3.StringUtils.trimToNull(String)
*
*
* @param str the String to be trimmed, may be null
* @return the trimmed String, {@code null} if only chars <= 32, empty or null String input
*/
public static String trimToNull(final String str) {
final String ts = str == null ? null : str.trim();
return isEmpty(ts) ? null : ts;
}
private Strings() {
// empty
}
/**
* Shorthand for {@code str.toLowerCase(Locale.ROOT);}
* @param str The string to upper case.
* @return a new string
* @see String#toLowerCase(Locale)
*/
public static String toRootLowerCase(final String str) {
return str.toLowerCase(Locale.ROOT);
}
/**
* Shorthand for {@code str.toUpperCase(Locale.ROOT);}
* @param str The string to lower case.
* @return a new string
* @see String#toLowerCase(Locale)
*/
public static String toRootUpperCase(final String str) {
return str.toUpperCase(Locale.ROOT);
}
/**
* Concatenates 2 Strings without allocation.
* @param str1 the first string.
* @param str2 the second string.
* @return the concatenated String.
*/
public static String concat(final String str1, final String str2) {
if (isEmpty(str1)) {
return str2;
} else if (isEmpty(str2)) {
return str1;
}
final StringBuilder sb = FORMAT_BUFFER_REF.get();
try {
return sb.append(str1).append(str2).toString();
} finally {
trimToMaxSize(sb, MAX_FORMAT_BUFFER_LENGTH);
sb.setLength(0);
}
}
/**
* Creates a new string repeating given {@code str} {@code count} times.
* @param str input string
* @param count the repetition count
* @return the new string
* @throws IllegalArgumentException if either {@code str} is null or {@code count} is negative
*/
public static String repeat(final String str, final int count) {
Objects.requireNonNull(str, "str");
if (count < 0) {
throw new IllegalArgumentException("count");
}
final StringBuilder sb = FORMAT_BUFFER_REF.get();
try {
for (int index = 0; index < count; index++) {
sb.append(str);
}
return sb.toString();
} finally {
trimToMaxSize(sb, MAX_FORMAT_BUFFER_LENGTH);
sb.setLength(0);
}
}
}