StringUtils.java
/**
*
* Copyright 2003-2007 Jive Software.
*
* Licensed 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.jivesoftware.smack.util;
import java.io.UnsupportedEncodingException;
import java.util.Collection;
import java.util.Random;
/**
* A collection of utility methods for String objects.
*/
public class StringUtils {
public static final String MD5 = "MD5";
public static final String SHA1 = "SHA-1";
public static final String UTF8 = "UTF-8";
public static final String USASCII = "US-ASCII";
public static final String QUOTE_ENCODE = """;
public static final String APOS_ENCODE = "'";
public static final String AMP_ENCODE = "&";
public static final String LT_ENCODE = "<";
public static final String GT_ENCODE = ">";
public static final char[] HEX_CHARS = "0123456789abcdef".toCharArray();
/**
* Escapes all necessary characters in the String so that it can be used
* in an XML doc.
*
* @param string the string to escape.
* @return the string with appropriate characters escaped.
*/
public static CharSequence escapeForXML(final String string) {
if (string == null) {
return null;
}
final char[] input = string.toCharArray();
final int len = input.length;
final StringBuilder out = new StringBuilder((int)(len*1.3));
CharSequence toAppend;
char ch;
int last = 0;
int i = 0;
while (i < len) {
toAppend = null;
ch = input[i];
switch(ch) {
case '<':
toAppend = LT_ENCODE;
break;
case '>':
toAppend = GT_ENCODE;
break;
case '&':
toAppend = AMP_ENCODE;
break;
case '"':
toAppend = QUOTE_ENCODE;
break;
case '\'':
toAppend = APOS_ENCODE;
break;
default:
break;
}
if (toAppend != null) {
if (i > last) {
out.append(input, last, i - last);
}
out.append(toAppend);
last = ++i;
} else {
i++;
}
}
if (last == 0) {
return string;
}
if (i > last) {
out.append(input, last, i - last);
}
return out;
}
/**
* Hashes a String using the SHA-1 algorithm and returns the result as a
* String of hexadecimal numbers. This method is synchronized to avoid
* excessive MessageDigest object creation. If calling this method becomes
* a bottleneck in your code, you may wish to maintain a pool of
* MessageDigest objects instead of using this method.
* <p>
* A hash is a one-way function -- that is, given an
* input, an output is easily computed. However, given the output, the
* input is almost impossible to compute. This is useful for passwords
* since we can store the hash and a hacker will then have a very hard time
* determining the original password.
*
* @param data the String to compute the hash of.
* @return a hashed version of the passed-in String
* @deprecated use {@link org.jivesoftware.smack.util.SHA1#hex(String)} instead.
*/
@Deprecated
public synchronized static String hash(String data) {
return org.jivesoftware.smack.util.SHA1.hex(data);
}
/**
* Encodes an array of bytes as String representation of hexadecimal.
*
* @param bytes an array of bytes to convert to a hex string.
* @return generated hex string.
*/
public static String encodeHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for ( int j = 0; j < bytes.length; j++ ) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = HEX_CHARS[v >>> 4];
hexChars[j * 2 + 1] = HEX_CHARS[v & 0x0F];
}
return new String(hexChars);
}
public static byte[] toBytes(String string) {
try {
return string.getBytes(StringUtils.UTF8);
}
catch (UnsupportedEncodingException e) {
throw new IllegalStateException("UTF-8 encoding not supported by platform", e);
}
}
/**
* Pseudo-random number generator object for use with randomString().
* The Random class is not considered to be cryptographically secure, so
* only use these random Strings for low to medium security applications.
*/
private static Random randGen = new Random();
/**
* Array of numbers and letters of mixed case. Numbers appear in the list
* twice so that there is a more equal chance that a number will be picked.
* We can use the array to get a random number or letter by picking a random
* array index.
*/
private static char[] numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyz" +
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
/**
* Returns a random String of numbers and letters (lower and upper case)
* of the specified length. The method uses the Random class that is
* built-in to Java which is suitable for low to medium grade security uses.
* This means that the output is only pseudo random, i.e., each number is
* mathematically generated so is not truly random.<p>
*
* The specified length must be at least one. If not, the method will return
* null.
*
* @param length the desired length of the random String to return.
* @return a random String of numbers and letters of the specified length.
*/
public static String randomString(int length) {
if (length < 1) {
return null;
}
// Create a char buffer to put random letters and numbers in.
char [] randBuffer = new char[length];
for (int i=0; i<randBuffer.length; i++) {
randBuffer[i] = numbersAndLetters[randGen.nextInt(numbersAndLetters.length)];
}
return new String(randBuffer);
}
/**
* Returns true if CharSequence is not null and is not empty, false otherwise
* Examples:
* isNotEmpty(null) - false
* isNotEmpty("") - false
* isNotEmpty(" ") - true
* isNotEmpty("empty") - true
*
* @param cs checked CharSequence
* @return true if string is not null and is not empty, false otherwise
*/
public static boolean isNotEmpty(CharSequence cs) {
return !isNullOrEmpty(cs);
}
/**
* Returns true if the given CharSequence is null or empty.
*
* @param cs
* @return true if the given CharSequence is null or empty
*/
public static boolean isNullOrEmpty(CharSequence cs) {
return cs == null || isEmpty(cs);
}
/**
* Returns true if the given CharSequence is empty
*
* @param cs
* @return true if the given CharSequence is empty
*/
public static boolean isEmpty(CharSequence cs) {
return cs.length() == 0;
}
public static String collectionToString(Collection<String> collection) {
StringBuilder sb = new StringBuilder();
for (String s : collection) {
sb.append(s);
sb.append(" ");
}
String res = sb.toString();
// Remove the trailing whitespace
res = res.substring(0, res.length() - 1);
return res;
}
public static String returnIfNotEmptyTrimmed(String string) {
if (string == null)
return null;
String trimmedString = string.trim();
if (trimmedString.length() > 0) {
return trimmedString;
} else {
return null;
}
}
public static boolean nullSafeCharSequenceEquals(CharSequence csOne, CharSequence csTwo) {
return nullSafeCharSequenceComperator(csOne, csTwo) == 0;
}
public static int nullSafeCharSequenceComperator(CharSequence csOne, CharSequence csTwo) {
if (csOne == null ^ csTwo == null) {
return (csOne == null) ? -1 : 1;
}
if (csOne == null && csTwo == null) {
return 0;
}
return csOne.toString().compareTo(csTwo.toString());
}
public static <CS extends CharSequence> CS requireNotNullOrEmpty(CS cs, String message) {
if (isNullOrEmpty(cs)) {
throw new IllegalArgumentException(message);
}
return cs;
}
/**
* Return the String representation of the given char sequence if it is not null.
*
* @param cs the char sequence or null.
* @return the String representation of <code>cs</code> or null.
*/
public static String maybeToString(CharSequence cs) {
if (cs == null) {
return null;
}
return cs.toString();
}
}