Finds the first index within a String, handling null. : String search « Data Type « Java
Finds the first index within a String, handling null.
/**
* 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.
*/
/**
* <p>Operations on {@link java.lang.String} that are
* <code>null</code> safe.</p>
*
* @see java.lang.String
* @author <a href="http://jakarta.apache.org/turbine/">Apache Jakarta Turbine</a>
* @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
* @author Daniel L. Rall
* @author <a href="mailto:gcoladonato@yahoo.com">Greg Coladonato</a>
* @author <a href="mailto:ed@apache.org">Ed Korthof</a>
* @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a>
* @author Stephen Colebourne
* @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a>
* @author Holger Krauth
* @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a>
* @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
* @author Arun Mammen Thomas
* @author Gary Gregory
* @author Phil Steitz
* @author Al Chou
* @author Michael Davey
* @author Reuben Sivan
* @author Chris Hyzer
* @author Scott Johnson
* @since 1.0
* @version $Id: StringUtils.java 635447 2008-03-10 06:27:09Z bayard $
*/
public class Main {
/**
* <p>Finds the first index within a String, handling <code>null</code>.
* This method uses {@link String#indexOf(String, int)}.</p>
*
* <p>A <code>null</code> String will return <code>-1</code>.
* A negative start position is treated as zero.
* An empty ("") search String always matches.
* A start position greater than the string length only matches
* an empty search String.</p>
*
* <pre>
* StringUtils.indexOf(null, *, *) = -1
* StringUtils.indexOf(*, null, *) = -1
* StringUtils.indexOf("", "", 0) = 0
* StringUtils.indexOf("aabaabaa", "a", 0) = 0
* StringUtils.indexOf("aabaabaa", "b", 0) = 2
* StringUtils.indexOf("aabaabaa", "ab", 0) = 1
* StringUtils.indexOf("aabaabaa", "b", 3) = 5
* StringUtils.indexOf("aabaabaa", "b", 9) = -1
* StringUtils.indexOf("aabaabaa", "b", -1) = 2
* StringUtils.indexOf("aabaabaa", "", 2) = 2
* StringUtils.indexOf("abc", "", 9) = 3
* </pre>
*
* @param str the String to check, may be null
* @param searchStr the String to find, may be null
* @param startPos the start position, negative treated as zero
* @return the first index of the search String,
* -1 if no match or <code>null</code> string input
* @since 2.0
*/
public static int indexOf(String str, String searchStr, int startPos) {
if (str == null || searchStr == null) {
return -1;
}
// JDK1.2/JDK1.3 have a bug, when startPos > str.length for "", hence
if (searchStr.length() == 0 && startPos >= str.length()) {
return str.length();
}
return str.indexOf(searchStr, startPos);
}
}
