stringtokenizer.java

对话解析实例的手机游戏编程序源代码

/*
 * @(#)StringTokenizer.java	1.29 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package cn.com.javachen;

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * The string tokenizer class allows an application to break a string into
 * tokens. The tokenization method is much simpler than the one used by the
 * <code>StreamTokenizer</code> class. The <code>StringTokenizer</code>
 * methods do not distinguish among identifiers, numbers, and quoted strings,
 * nor do they recognize and skip comments.
 * <p>
 * The set of delimiters (the characters that separate tokens) may be specified
 * either at creation time or on a per-token basis.
 * <p>
 * An instance of <code>StringTokenizer</code> behaves in one of two ways,
 * depending on whether it was created with the <code>returnDelims</code> flag
 * having the value <code>true</code> or <code>false</code>:
 * <ul>
 * <li>If the flag is <code>false</code>, delimiter characters serve to
 * separate tokens. A token is a maximal sequence of consecutive characters that
 * are not delimiters.
 * <li>If the flag is <code>true</code>, delimiter characters are themselves
 * considered to be tokens. A token is thus either one delimiter character, or a
 * maximal sequence of consecutive characters that are not delimiters.
 * </ul>
 * <p>
 * A <tt>StringTokenizer</tt> object internally maintains a current position
 * within the string to be tokenized. Some operations advance this current
 * position past the characters processed.
 * <p>
 * A token is returned by taking a substring of the string that was used to
 * create the <tt>StringTokenizer</tt> object.
 * <p>
 * The following is one example of the use of the tokenizer. The code:
 * <blockquote>
 * 
 * <pre>
 * StringTokenizer st = new StringTokenizer(&quot;this is a test&quot;);
 * while (st.hasMoreTokens()) {
 * 	System.out.println(st.nextToken());
 * }
 * </pre>
 * 
 * </blockquote>
 * <p>
 * prints the following output: <blockquote>
 * 
 * <pre>
 *      this
 *      is
 *      a
 *      test
 * </pre>
 * 
 * </blockquote>
 * 
 * <p>
 * <tt>StringTokenizer</tt> is a legacy class that is retained for
 * compatibility reasons although its use is discouraged in new code. It is
 * recommended that anyone seeking this functionality use the <tt>split</tt>
 * method of <tt>String</tt> or the java.util.regex package instead.
 * <p>
 * The following example illustrates how the <tt>String.split</tt> method can
 * be used to break up a string into its basic tokens: <blockquote>
 * 
 * <pre>
 * String[] result = &quot;this is a test&quot;.split(&quot;\\s&quot;);
 * for (int x = 0; x &lt; result.length; x++)
 * 	System.out.println(result[x]);
 * </pre>
 * 
 * </blockquote>
 * <p>
 * prints the following output: <blockquote>
 * 
 * <pre>
 *      this
 *      is
 *      a
 *      test
 * </pre>
 * 
 * </blockquote>
 * 
 * @author unascribed
 * @version 1.29, 01/23/03
 * @see java.io.StreamTokenizer
 * @since JDK1.0
 */
public class StringTokenizer implements Enumeration {
	private int currentPosition;

	private int newPosition;

	private int maxPosition;

	private String str;

	private String delimiters;

	private boolean retDelims;

	private boolean delimsChanged;

	/**
	 * maxDelimChar stores the value of the delimiter character with the highest
	 * value. It is used to optimize the detection of delimiter characters.
	 */
	private char maxDelimChar;

	/**
	 * Set maxDelimChar to the highest char in the delimiter set.
	 */
	private void setMaxDelimChar() {
		if (delimiters == null) {
			maxDelimChar = 0;
			return;
		}

		char m = 0;
		for (int i = 0; i < delimiters.length(); i++) {
			char c = delimiters.charAt(i);
			if (m < c)
				m = c;
		}
		maxDelimChar = m;
	}

	/**
	 * Constructs a string tokenizer for the specified string. All characters in
	 * the <code>delim</code> argument are the delimiters for separating
	 * tokens.
	 * <p>
	 * If the <code>returnDelims</code> flag is <code>true</code>, then the
	 * delimiter characters are also returned as tokens. Each delimiter is
	 * returned as a string of length one. If the flag is <code>false</code>,
	 * the delimiter characters are skipped and only serve as separators between
	 * tokens.
	 * <p>
	 * Note that if <tt>delim</tt> is <tt>null</tt>, this constructor does
	 * not throw an exception. However, trying to invoke other methods on the
	 * resulting <tt>StringTokenizer</tt> may result in a
	 * <tt>NullPointerException</tt>.
	 * 
	 * @param str
	 *            a string to be parsed.
	 * @param delim
	 *            the delimiters.
	 * @param returnDelims
	 *            flag indicating whether to return the delimiters as tokens.
	 */
	public StringTokenizer(String str, String delim, boolean returnDelims) {
		currentPosition = 0;
		newPosition = -1;
		delimsChanged = false;
		this.str = str;
		maxPosition = str.length();
		delimiters = delim;
		retDelims = returnDelims;
		setMaxDelimChar();
	}

	/**
	 * Constructs a string tokenizer for the specified string. The characters in
	 * the <code>delim</code> argument are the delimiters for separating
	 * tokens. Delimiter characters themselves will not be treated as tokens.
	 * 
	 * @param str
	 *            a string to be parsed.
	 * @param delim
	 *            the delimiters.
	 */
	public StringTokenizer(String str, String delim) {
		this(str, delim, false);
	}

	/**
	 * Constructs a string tokenizer for the specified string. The tokenizer
	 * uses the default delimiter set, which is
	 * <code>"&nbsp;&#92;t&#92;n&#92;r&#92;f"</code>: the space character,
	 * the tab character, the newline character, the carriage-return character,
	 * and the form-feed character. Delimiter characters themselves will not be
	 * treated as tokens.
	 * 
	 * @param str
	 *            a string to be parsed.
	 */
	public StringTokenizer(String str) {
		this(str, " \t\n\r\f", false);
	}

	/**
	 * Skips delimiters starting from the specified position. If retDelims is
	 * false, returns the index of the first non-delimiter character at or after
	 * startPos. If retDelims is true, startPos is returned.
	 */
	private int skipDelimiters(int startPos) {
		if (delimiters == null)
			throw new NullPointerException();

		int position = startPos;
		while (!retDelims && position < maxPosition) {
			char c = str.charAt(position);
			if ((c > maxDelimChar) || (delimiters.indexOf(c) < 0))
				break;
			position++;
		}
		return position;
	}

	/**
	 * Skips ahead from startPos and returns the index of the next delimiter
	 * character encountered, or maxPosition if no such delimiter is found.
	 */
	private int scanToken(int startPos) {
		int position = startPos;
		while (position < maxPosition) {
			char c = str.charAt(position);
			if ((c <= maxDelimChar) && (delimiters.indexOf(c) >= 0))
				break;
			position++;
		}
		if (retDelims && (startPos == position)) {
			char c = str.charAt(position);
			if ((c <= maxDelimChar) && (delimiters.indexOf(c) >= 0))
				position++;
		}
		return position;
	}

	/**
	 * Tests if there are more tokens available from this tokenizer's string. If
	 * this method returns <tt>true</tt>, then a subsequent call to
	 * <tt>nextToken</tt> with no argument will successfully return a token.
	 * 
	 * @return <code>true</code> if and only if there is at least one token in
	 *         the string after the current position; <code>false</code>
	 *         otherwise.
	 */
	public boolean hasMoreTokens() {
		/*
		 * Temporary store this position and use it in the following nextToken()
		 * method only if the delimiters have'nt been changed in that
		 * nextToken() invocation.
		 */
		newPosition = skipDelimiters(currentPosition);
		return (newPosition < maxPosition);
	}

	/**
	 * Returns the next token from this string tokenizer.
	 * 
	 * @return the next token from this string tokenizer.
	 * @exception NoSuchElementException
	 *                if there are no more tokens in this tokenizer's string.
	 */
	public String nextToken() {
		/*
		 * If next position already computed in hasMoreElements() and delimiters
		 * have changed between the computation and this invocation, then use
		 * the computed value.
		 */

		currentPosition = (newPosition >= 0 && !delimsChanged) ? newPosition
				: skipDelimiters(currentPosition);

		/* Reset these anyway */
		delimsChanged = false;
		newPosition = -1;

		if (currentPosition >= maxPosition)
			throw new NoSuchElementException();
		int start = currentPosition;
		currentPosition = scanToken(currentPosition);
		return str.substring(start, currentPosition);
	}

	/**
	 * Returns the next token in this string tokenizer's string. First, the set
	 * of characters considered to be delimiters by this
	 * <tt>StringTokenizer</tt> object is changed to be the characters in the
	 * string <tt>delim</tt>. Then the next token in the string after the
	 * current position is returned. The current position is advanced beyond the
	 * recognized token. The new delimiter set remains the default after this
	 * call.
	 * 
	 * @param delim
	 *            the new delimiters.
	 * @return the next token, after switching to the new delimiter set.
	 * @exception NoSuchElementException
	 *                if there are no more tokens in this tokenizer's string.
	 */
	public String nextToken(String delim) {
		delimiters = delim;

		/* delimiter string specified, so set the appropriate flag. */
		delimsChanged = true;

		setMaxDelimChar();
		return nextToken();
	}

	/**
	 * Returns the same value as the <code>hasMoreTokens</code> method. It
	 * exists so that this class can implement the <code>Enumeration</code>
	 * interface.
	 * 
	 * @return <code>true</code> if there are more tokens; <code>false</code>
	 *         otherwise.
	 * @see java.util.Enumeration
	 * @see java.util.StringTokenizer#hasMoreTokens()
	 */
	public boolean hasMoreElements() {
		return hasMoreTokens();
	}

	/**
	 * Returns the same value as the <code>nextToken</code> method, except
	 * that its declared return value is <code>Object</code> rather than
	 * <code>String</code>. It exists so that this class can implement the
	 * <code>Enumeration</code> interface.
	 * 
	 * @return the next token in the string.
	 * @exception NoSuchElementException
	 *                if there are no more tokens in this tokenizer's string.
	 * @see java.util.Enumeration
	 * @see java.util.StringTokenizer#nextToken()
	 */
	public Object nextElement() {
		return nextToken();
	}

	/**
	 * Calculates the number of times that this tokenizer's
	 * <code>nextToken</code> method can be called before it generates an
	 * exception. The current position is not advanced.
	 * 
	 * @return the number of tokens remaining in the string using the current
	 *         delimiter set.
	 * @see java.util.StringTokenizer#nextToken()
	 */
	public int countTokens() {
		int count = 0;
		int currpos = currentPosition;
		while (currpos < maxPosition) {
			currpos = skipDelimiters(currpos);
			if (currpos >= maxPosition)
				break;
			currpos = scanToken(currpos);
			count++;
		}
		return count;
	}
}