StringUtils.java
/*
* 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.tika.utils;
import java.util.List;
public class StringUtils {
/**
* The empty String {@code ""}.
*
* @since 2.0
*/
public static final String EMPTY = "";
/**
* A String for a space character.
*
* @since 3.2
*/
public static final String SPACE = " ";
static int PAD_LIMIT = 10000;
public static boolean isEmpty(final CharSequence cs) {
return cs == null || cs.isEmpty();
}
public static boolean isBlank(final String s) {
return s == null || s.isBlank();
}
/**
* <p>Left pad a String with a specified String.</p>
*
* <p>Pad to a size of {@code size}.</p>
*
* <pre>
* StringUtils.leftPad(null, *, *) = null
* StringUtils.leftPad("", 3, "z") = "zzz"
* StringUtils.leftPad("bat", 3, "yz") = "bat"
* StringUtils.leftPad("bat", 5, "yz") = "yzbat"
* StringUtils.leftPad("bat", 8, "yz") = "yzyzybat"
* StringUtils.leftPad("bat", 1, "yz") = "bat"
* StringUtils.leftPad("bat", -1, "yz") = "bat"
* StringUtils.leftPad("bat", 5, null) = " bat"
* StringUtils.leftPad("bat", 5, "") = " bat"
* </pre>
*
* @param str the String to pad out, may be null
* @param size the size to pad to
* @param padStr the String to pad with, null or empty treated as single space
* @return left padded String or original String if no padding is necessary,
* {@code null} if null String input
*/
public static String leftPad(final String str, final int size, String padStr) {
if (str == null) {
return null;
}
if (isEmpty(padStr)) {
padStr = SPACE;
}
final int padLen = padStr.length();
final int strLen = str.length();
final int pads = size - strLen;
if (pads <= 0) {
return str; // returns original String when possible
}
if (padLen == 1 && pads <= PAD_LIMIT) {
return leftPad(str, size, padStr.charAt(0));
}
if (pads == padLen) {
return padStr.concat(str);
} else if (pads < padLen) {
return padStr.substring(0, pads).concat(str);
} else {
final char[] padding = new char[pads];
final char[] padChars = padStr.toCharArray();
for (int i = 0; i < pads; i++) {
padding[i] = padChars[i % padLen];
}
return new String(padding).concat(str);
}
}
public static String leftPad(final String str, final int size, final char padChar) {
if (str == null) {
return null;
}
final int pads = size - str.length();
if (pads <= 0) {
return str; // returns original String when possible
}
if (pads > PAD_LIMIT) {
return leftPad(str, size, String.valueOf(padChar));
}
return repeat(padChar, pads).concat(str);
}
/**
* <p>Returns padding using the specified delimiter repeated
* to a given length.</p>
*
* <pre>
* StringUtils.repeat('e', 0) = ""
* StringUtils.repeat('e', 3) = "eee"
* StringUtils.repeat('e', -2) = ""
* </pre>
*
* <p>Note: this method does not support padding with
* <a href="http://www.unicode.org/glossary/#supplementary_character">Unicode Supplementary Characters</a>
* as they require a pair of {@code char}s to be represented.
* If you are needing to support full I18N of your applications
* consider using {@link #repeat(String, int)} instead.
* </p>
*
* @param ch character to repeat
* @param repeat number of times to repeat char, negative treated as zero
* @return String with repeated character
* @see #repeat(String, int)
*/
public static String repeat(final char ch, final int repeat) {
if (repeat <= 0) {
return EMPTY;
}
final char[] buf = new char[repeat];
for (int i = repeat - 1; i >= 0; i--) {
buf[i] = ch;
}
return new String(buf);
}
// Padding
//-----------------------------------------------------------------------
/**
* <p>Repeat a String {@code repeat} times to form a
* new String.</p>
*
* <pre>
* StringUtils.repeat(null, 2) = null
* StringUtils.repeat("", 0) = ""
* StringUtils.repeat("", 2) = ""
* StringUtils.repeat("a", 3) = "aaa"
* StringUtils.repeat("ab", 2) = "abab"
* StringUtils.repeat("a", -2) = ""
* </pre>
*
* @param str the String to repeat, may be null
* @param repeat number of times to repeat str, negative treated as zero
* @return a new String consisting of the original String repeated,
* {@code null} if null String input
*/
public static String repeat(final String str, final int repeat) {
// Performance tuned for 2.0 (JDK1.4)
if (str == null) {
return null;
}
if (repeat <= 0) {
return EMPTY;
}
final int inputLength = str.length();
if (repeat == 1 || inputLength == 0) {
return str;
}
if (inputLength == 1 && repeat <= PAD_LIMIT) {
return repeat(str.charAt(0), repeat);
}
final int outputLength = inputLength * repeat;
switch (inputLength) {
case 1:
return repeat(str.charAt(0), repeat);
case 2:
final char ch0 = str.charAt(0);
final char ch1 = str.charAt(1);
final char[] output2 = new char[outputLength];
for (int i = repeat * 2 - 2; i >= 0; i--, i--) {
output2[i] = ch0;
output2[i + 1] = ch1;
}
return new String(output2);
default:
final StringBuilder buf = new StringBuilder(outputLength);
for (int i = 0; i < repeat; i++) {
buf.append(str);
}
return buf.toString();
}
}
public static String joinWith(String delimiter, List<String> lines) {
if (lines.size() == 0) {
return EMPTY;
}
int i = 0;
StringBuilder sb = new StringBuilder();
for (String line : lines) {
if (i++ > 0) {
sb.append(delimiter);
}
sb.append(line);
}
return sb.toString();
}
}