charsetutils.java

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package org.apache.commons.lang;

/**
 * <p>Operations on <code>CharSet</code>s.</p>
 *
 * <p>This class handles <code>null</code> input gracefully.
 * An exception will not be thrown for a <code>null</code> input.
 * Each method documents its behaviour in more detail.</p>
 * 
 * @see CharSet
 * @author <a href="[e-mail]">Henri Yandell</a>
 * @author Stephen Colebourne
 * @author Phil Steitz
 * @author Gary Gregory
 * @since 1.0
 * @version $Id: CharSetUtils.java,v 1.26 2003/08/22 17:25:33 ggregory Exp $
 */
public class CharSetUtils {

    /**
     * <p>CharSetUtils instances should NOT be constructed in standard programming.
     * Instead, the class should be used as <code>CharSetUtils.evaluateSet(null);</code>.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean instance
     * to operate.</p>
     */
    public CharSetUtils() {
    }

    // Factory
    //-----------------------------------------------------------------------
    /**
     * <p>Creates a <code>CharSet</code> instance which allows a certain amount of
     * set logic to be performed.</p>
     * <p>The syntax is:</p>
     * <ul>
     *  <li>&quot;aeio&quot; which implies 'a','e',..</li>
     *  <li>&quot;^e&quot; implies not e.</li>
     *  <li>&quot;ej-m&quot; implies e,j->m. e,j,k,l,m.</li>
     * </ul>
     * 
     * <pre>
     * CharSetUtils.evaluateSet(null)    = null
     * CharSetUtils.evaluateSet([])      = CharSet matching nothing
     * CharSetUtils.evaluateSet(["a-e"]) = CharSet matching a,b,c,d,e
     * </pre>
     *
     * @param set  the set, may be null
     * @return a CharSet instance, <code>null</code> if null input
     * @deprecated Use {@link CharSet#getInstance(String)}.
     *             Method will be removed in Commons Lang 3.0.
     */
    public static CharSet evaluateSet(String[] set) {
        if (set == null) {
            return null;
        }
        return new CharSet(set); 
    }

    // Squeeze
    //-----------------------------------------------------------------------
    /**
     * <p>Squeezes any repititions of a character that is mentioned in the
     * supplied set.</p>
     *
     * <pre>
     * CharSetUtils.squeeze(null, *)        = null
     * CharSetUtils.squeeze("", *)          = ""
     * CharSetUtils.squeeze(*, null)        = *
     * CharSetUtils.squeeze(*, "")          = *
     * CharSetUtils.squeeze("hello", "k-p") = "helo"
     * CharSetUtils.squeeze("hello", "a-e") = "hello"
     * </pre>
     *
     * @see #evaluateSet(java.lang.String[]) for set-syntax.
     * @param str  the string to squeeze, may be null
     * @param set  the character set to use for manipulation, may be null
     * @return modified String, <code>null</code> if null string input
     */
    public static String squeeze(String str, String set) {
        if (str == null || str.length() == 0 || set == null || set.length() == 0) {
            return str;
        }
        String[] strs = new String[1];
        strs[0] = set;
        return squeeze(str, strs);
    }

    /**
     * <p>Squeezes any repititions of a character that is mentioned in the
     * supplied set.</p>
     *
     * <p>An example is:</p>
     * <ul>
     *   <li>squeeze(&quot;hello&quot;, {&quot;el&quot;}) => &quot;helo&quot;</li>
     * </ul>
     * 
     * @see #evaluateSet(java.lang.String[]) for set-syntax.
     * @param str  the string to squeeze, may be null
     * @param set  the character set to use for manipulation, may be null
     * @return modified String, <code>null</code> if null string input
     */
    public static String squeeze(String str, String[] set) {
        if (str == null || str.length() == 0 || set == null || set.length == 0) {
            return str;
        }
        CharSet chars = evaluateSet(set);
        StringBuffer buffer = new StringBuffer(str.length());
        char[] chrs = str.toCharArray();
        int sz = chrs.length;
        char lastChar = ' ';
        char ch = ' ';
        for (int i = 0; i < sz; i++) {
            ch = chrs[i];
            if (chars.contains(ch)) {
                if ((ch == lastChar) && (i != 0)) {
                    continue;
                }
            }
            buffer.append(ch);
            lastChar = ch;
        }
        return buffer.toString();
    }

    // Count
    //-----------------------------------------------------------------------
    /**
     * <p>Takes an argument in set-syntax, see evaluateSet,
     * and returns the number of characters present in the specified string.</p>
     *
     * <pre>
     * CharSetUtils.count(null, *)        = 0
     * CharSetUtils.count("", *)          = 0
     * CharSetUtils.count(*, null)        = 0
     * CharSetUtils.count(*, "")          = 0
     * CharSetUtils.count("hello", "k-p") = 3
     * CharSetUtils.count("hello", "a-e") = 1
     * </pre>
     *
     * @see #evaluateSet(java.lang.String[]) for set-syntax.
     * @param str  String to count characters in, may be null
     * @param set  String set of characters to count, may be null
     * @return character count, zero if null string input
     */
    public static int count(String str, String set) {
        if (str == null || str.length() == 0 || set == null || set.length() == 0) {
            return 0;
        }
        String[] strs = new String[1];
        strs[0] = set;
        return count(str, strs);
    }
    
    /**
     * <p>Takes an argument in set-syntax, see evaluateSet,