src/java/org/apache/commons/lang/CharRange.java

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package org.apache.commons.lang;

/**
 * <p>A range of characters. Able to understand the idea of a contiguous
 * sublist of an alphabet, a negated concept, and a set of characters.</p>
 *
 * <p>Used by <code>CharSet</code> to handle sets of characters.</p>
 *
 * @author <a href="bayard@generationjava.com">Henri Yandell</a>
 * @author Stephen Colebourne
 * @since 1.0
 * @version $Id: CharRange.java,v 1.7 2003/07/16 00:39:05 scolebourne Exp $
 */
class CharRange {

    /**
     * <p>Used internally to represent <code>null</code> in a char.</p>
     */
    private static char UNSET;

    private char start;
    private char close;
    private boolean negated;

    /**
     * <p>Construct a <code>CharRange</code> over a single character.</p>
     *
     * @param start char over which this range is placed
     */
    public CharRange(char start) {
        this.start = start;
    }

    /**
     * <p>Construct a <code>CharRange</code> over a set of characters.</p>
     *
     * @param start  char start character in this range. inclusive
     * @param close  char close character in this range. inclusive
     */
    public CharRange(char start, char close) {
        this.start = start;
        this.close = close;
    }

    /**
     * <p>Construct a <code>CharRange</code> over a set of characters.</p>
     *
     * @param start  String start first character is in this range (inclusive).
     * @param close  String first character is close character in this
     *  range (inclusive).
     * @throws NullPointerException if either String is <code>null</code>
     */
    public CharRange(String start, String close) {
        this.start = start.charAt(0);
        this.close = close.charAt(0);
    }

    /**
     * <p>Get the start character for this character range.</p>
     * 
     * @return start char (inclusive)
     */
    public char getStart() {
        return this.start;
    }

    /**
     * <p>Get the end character for this character range.</p>
     * 
     * @return end char (inclusive)
     */
    public char getEnd() {
        return this.close;
    }

    /**
     * <p>Set the start character for this character range.</p>
     * 
     * @param ch  start char (inclusive)
     */
    public void setStart(char ch) {
        this.start = ch;
    }

    /**
     * <p>Set the end character for this character range.</p>
     * 
     * @param ch  start char (inclusive)
     */
    public void setEnd(char ch) {
        this.close = ch;
    }

    /**
     * <p>Is this <code>CharRange</code> over many characters.</p>
     *
     * @return boolean <code>true</code> is many characters
     */
    public boolean isRange() {
        return this.close != UNSET;
    }

    /**
     * <p>Is the passed in character <code>ch</code> inside
     * this range.</p>
     *
     * @param ch character to test for
     * @return boolean <code>true</code> is in range
     */
    public boolean inRange(char ch) {
        if( isRange() ) {
            return ((ch >= start) && (ch <= close));
        } else {
            return start == ch;
        }
    }

    /**
     * <p>Checks if this <code>CharRange</code> is negated.</p>
     *
     * @return boolean <code>true</code> is negated
     */
    public boolean isNegated() {
        return negated;
    }

    /**
     * <p>Sets this character range to be negated or not.</p>
     *
     * <p>This implies that this <code>CharRange</code> is over
     * all characters except the ones in this range.</p>
     * 
     * @param negated  <code>true</code> to negate the range
     */
    public void setNegated(boolean negated) {
        this.negated = negated;
    }

    /**
     * <p>Output a string representation of the character range.</p>
     * 
     * @return string representation
     */
    public String toString() {
        String str = "";
        if( isNegated() ) {
            str += "^";
        }
        str += start;
        if( isRange() ) {
            str += "-";
            str += close;
        }
        return str;
    }
    
}