Gets the String that is nested in between two instances of the same String. A null input String returns null. - Java java.lang

Description

Gets the String that is nested in between two instances of the same String. A null input String returns null.

Demo Code

/*/*from w w  w .ja va2 s.co m*/
 * Copyright 2013 Guidewire Software, Inc.
 */
/**
 * This class is based, in part, on org.apache.commons.lang.StringUtils and is intended
 * to break the dependency on that project.
 *
 * @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
 *  Johnson

 */
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Collection;
import java.util.ArrayList;
import java.util.Formatter;
import java.util.List;
import java.util.Iterator;
import java.util.Locale;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Main{
    public static void main(String[] argv){
        String str = "java2s.com";
        String tag = "java2s.com";
        System.out.println(getNestedString(str,tag));
    }
    /**
     * The empty String <code>""</code>.
     * @since 2.0
     */
    public static final String EMPTY = "";
    /**
     * <p>Gets the String that is nested in between two instances of the
     * same String.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * A <code>null</code> tag returns <code>null</code>.</p>
     *
     * <pre>
     * getNestedString(null, *)            = null
     * getNestedString("", "")             = ""
     * getNestedString("", "tag")          = null
     * getNestedString("tagabctag", null)  = null
     * getNestedString("tagabctag", "")    = ""
     * getNestedString("tagabctag", "tag") = "abc"
     * </pre>
     *
     * @param str  the String containing nested-string, may be null
     * @param tag  the String before and after nested-string, may be null
     * @return the nested String, <code>null</code> if no match
     * @deprecated Use the better named {@link #substringBetween(String, String)}.
     *             Method will be removed in Commons Lang 3.0.
     */
    public static String getNestedString(String str, String tag) {
        return substringBetween(str, tag, tag);
    }
    /**
     * <p>Gets the String that is nested in between two Strings.
     * Only the first match is returned.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * A <code>null</code> open/close returns <code>null</code> (no match).
     * An empty ("") open/close returns an empty string.</p>
     *
     * <pre>
     * getNestedString(null, *, *)          = null
     * getNestedString("", "", "")          = ""
     * getNestedString("", "", "tag")       = null
     * getNestedString("", "tag", "tag")    = null
     * getNestedString("yabcz", null, null) = null
     * getNestedString("yabcz", "", "")     = ""
     * getNestedString("yabcz", "y", "z")   = "abc"
     * getNestedString("yabczyabcz", "y", "z")   = "abc"
     * </pre>
     *
     * @param str  the String containing nested-string, may be null
     * @param open  the String before nested-string, may be null
     * @param close  the String after nested-string, may be null
     * @return the nested String, <code>null</code> if no match
     * @deprecated Use the better named {@link #substringBetween(String, String, String)}.
     *             Method will be removed in Commons Lang 3.0.
     */
    public static String getNestedString(String str, String open,
            String close) {
        return substringBetween(str, open, close);
    }
    /**
     * <p>Gets the String that is nested in between two instances of the
     * same String.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * A <code>null</code> tag returns <code>null</code>.</p>
     *
     * <pre>
     * substringBetween(null, *)            = null
     * substringBetween("", "")             = ""
     * substringBetween("", "tag")          = null
     * substringBetween("tagabctag", null)  = null
     * substringBetween("tagabctag", "")    = ""
     * substringBetween("tagabctag", "tag") = "abc"
     * </pre>
     *
     * @param str  the String containing the substring, may be null
     * @param tag  the String before and after the substring, may be null
     * @return the substring, <code>null</code> if no match
     * @since 2.0
     */
    public static String substringBetween(String str, String tag) {
        return substringBetween(str, tag, tag);
    }
    /**
     * <p>Gets the String that is nested in between two Strings.
     * Only the first match is returned.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * A <code>null</code> open/close returns <code>null</code> (no match).
     * An empty ("") open and close returns an empty string.</p>
     *
     * <pre>
     * substringBetween("wx[b]yz", "[", "]") = "b"
     * substringBetween(null, *, *)          = null
     * substringBetween(*, null, *)          = null
     * substringBetween(*, *, null)          = null
     * substringBetween("", "", "")          = ""
     * substringBetween("", "", "]")         = null
     * substringBetween("", "[", "]")        = null
     * substringBetween("yabcz", "", "")     = ""
     * substringBetween("yabcz", "y", "z")   = "abc"
     * substringBetween("yabczyabcz", "y", "z")   = "abc"
     * </pre>
     *
     * @param str  the String containing the substring, may be null
     * @param open  the String before the substring, may be null
     * @param close  the String after the substring, may be null
     * @return the substring, <code>null</code> if no match
     * @since 2.0
     */
    public static String substringBetween(String str, String open,
            String close) {
        if (str == null || open == null || close == null) {
            return null;
        }
        int start = str.indexOf(open);
        if (start != -1) {
            int end = str.indexOf(close, start + open.length());
            if (end != -1) {
                return str.substring(start + open.length(), end);
            }
        }
        return null;
    }
    /**
     * <p>Finds the first index within a String, handling <code>null</code>.
     * This method uses {@link String#indexOf(int)}.</p>
     *
     * <p>A <code>null</code> or empty ("") String will return <code>-1</code>.</p>
     *
     * <pre>
     * indexOf(null, *)         = -1
     * indexOf("", *)           = -1
     * indexOf("aabaabaa", 'a') = 0
     * indexOf("aabaabaa", 'b') = 2
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param searchChar  the character to find
     * @return the first index of the search character,
     *  -1 if no match or <code>null</code> string input
     * @since 2.0
     */
    public static int indexOf(String str, char searchChar) {
      if (str==null || str.equals("")) {
            return -1;
        }
        return str.indexOf(searchChar);
    }
    /**
     * <p>Finds the first index within a String from a start position,
     * handling <code>null</code>.
     * This method uses {@link String#indexOf(int, int)}.</p>
     *
     * <p>A <code>null</code> or empty ("") String will return <code>-1</code>.
     * A negative start position is treated as zero.
     * A start position greater than the string length returns <code>-1</code>.</p>
     *
     * <pre>
     * indexOf(null, *, *)          = -1
     * indexOf("", *, *)            = -1
     * indexOf("aabaabaa", 'b', 0)  = 2
     * indexOf("aabaabaa", 'b', 3)  = 5
     * indexOf("aabaabaa", 'b', 9)  = -1
     * indexOf("aabaabaa", 'b', -1) = 2
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param searchChar  the character to find
     * @param startPos  the start position, negative treated as zero
     * @return the first index of the search character,
     *  -1 if no match or <code>null</code> string input
     * @since 2.0
     */
    public static int indexOf(String str, char searchChar, int startPos) {
        if (str==null || str.equals("")) {
            return -1;
        }
        return str.indexOf(searchChar, startPos);
    }
    /**
     * <p>Finds the first index within a String, handling <code>null</code>.
     * This method uses {@link String#indexOf(String)}.</p>
     *
     * <p>A <code>null</code> String will return <code>-1</code>.</p>
     *
     * <pre>
     * indexOf(null, *)          = -1
     * indexOf(*, null)          = -1
     * indexOf("", "")           = 0
     * indexOf("aabaabaa", "a")  = 0
     * indexOf("aabaabaa", "b")  = 2
     * indexOf("aabaabaa", "ab") = 1
     * indexOf("aabaabaa", "")   = 0
     * </pre>
     *
     * @param str  the String to check, may be null
     * @param searchStr  the String to find, may be null
     * @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) {
        if (str == null || searchStr == null) {
            return -1;
        }
        return str.indexOf(searchStr);
    }
    /**
     * <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>
     * indexOf(null, *, *)          = -1
     * indexOf(*, null, *)          = -1
     * indexOf("", "", 0)           = 0
     * indexOf("aabaabaa", "a", 0)  = 0
     * indexOf("aabaabaa", "b", 0)  = 2
     * indexOf("aabaabaa", "ab", 0) = 1
     * indexOf("aabaabaa", "b", 3)  = 5
     * indexOf("aabaabaa", "b", 9)  = -1
     * indexOf("aabaabaa", "b", -1) = 2
     * indexOf("aabaabaa", "", 2)   = 2
     * 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);
    }
    /**
     * Gets a String's length or <code>0</code> if the String is <code>null</code>.
     *
     * @param str
     *            a String or <code>null</code>
     * @return String length or <code>0</code> if the String is <code>null</code>.
     * @since 2.4
     */
    public static int length(String str) {
        return str == null ? 0 : str.length();
    }
    /**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start <code>n</code>
     * characters from the end of the String.</p>
     *
     * <p>A <code>null</code> String will return <code>null</code>.
     * An empty ("") String will return "".</p>
     *
     * <pre>
     * substring(null, *)   = null
     * substring("", *)     = ""
     * substring("abc", 0)  = "abc"
     * substring("abc", 2)  = "c"
     * substring("abc", 4)  = ""
     * substring("abc", -2) = "bc"
     * substring("abc", -4) = "abc"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position, <code>null</code> if null String input
     */
    public static String substring(String str, int start) {
        if (str == null) {
            return null;
        }

        // handle negatives, which means last n characters
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        if (start < 0) {
            start = 0;
        }
        if (start > str.length()) {
            return EMPTY;
        }

        return str.substring(start);
    }
    /**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start/end <code>n</code>
     * characters from the end of the String.</p>
     *
     * <p>The returned substring starts with the character in the <code>start</code>
     * position and ends before the <code>end</code> position. All position counting is
     * zero-based -- i.e., to start at the beginning of the string use
     * <code>start = 0</code>. Negative start and end positions can be used to
     * specify offsets relative to the end of the String.</p>
     *
     * <p>If <code>start</code> is not strictly to the left of <code>end</code>, ""
     * is returned.</p>
     *
     * <pre>
     * substring(null, *, *)    = null
     * substring("", * ,  *)    = "";
     * substring("abc", 0, 2)   = "ab"
     * substring("abc", 2, 0)   = ""
     * substring("abc", 2, 4)   = "c"
     * substring("abc", 4, 6)   = ""
     * substring("abc", 2, 2)   = ""
     * substring("abc", -2, -1) = "b"
     * substring("abc", -4, 2)  = "ab"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @param end  the position to end at (exclusive), negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position to end positon,
     *  <code>null</code> if null String input
     */
    public static String substring(String str, int start, int end) {
        if (str == null) {
            return null;
        }

        // handle negatives
        if (end < 0) {
            end = str.length() + end; // remember end is negative
        }
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        // check length next
        if (end > str.length()) {
            end = str.length();
        }

        // if start is greater than end, return ""
        if (start > end) {
            return EMPTY;
        }

        if (start < 0) {
            start = 0;
        }
        if (end < 0) {
            end = 0;
        }

        return str.substring(start, end);
    }
}

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