Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/lang/StringBuffer.java

Java Source | 1998-03-20 | 27.3 KB | 774 lines

/*
 * @(#)StringBuffer.java    1.39 98/03/18
 *
 * Copyright 1994-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.lang;

/**
 * A string buffer implements a mutable sequence of characters.
 * <p>
 * String buffers are safe for use by multiple threads. The methods
 * are synchronized where necessary so that all the operations on any
 * particular instance behave as if they occur in some serial order.
 * <p>
 * String buffers are used by the compiler to implement the binary
 * string concatenation operator <code>+</code>. For example, the code:
 * <p><blockquote><pre>
 *     x = "a" + 4 + "c"
 * </pre></blockquote><p>
 * is compiled to the equivalent of:
 * <p><blockquote><pre>
 *     x = new StringBuffer().append("a").append(4).append("c")
 *                           .toString()
 * </pre></blockquote><p>
 * The principal operations on a <code>StringBuffer</code> are the
 * <code>append</code> and <code>insert</code> methods, which are
 * overloaded so as to accept data of any type. Each effectively
 * converts a given datum to a string and then appends or inserts the
 * characters of that string to the string buffer. The
 * <code>append</code> method always adds these characters at the end
 * of the buffer; the <code>insert</code> method adds the characters at
 * a specified point.
 * <p>
 * For example, if <code>z</code> refers to a string buffer object
 * whose current contents are "<code>start</code>", then
 * the method call <code>z.append("le")</code> would cause the string
 * buffer to contain "<code>startle</code>", whereas
 * <code>z.insert(4, "le")</code> would alter the string buffer to
 * contain "<code>starlet</code>".
 * <p>
 * Every string buffer has a capacity. As long as the length of the
 * character sequence contained in the string buffer does not exceed
 * the capacity, it is not necessary to allocate a new internal
 * buffer array. If the internal buffer overflows, it is
 * automatically made larger.
 *
 * @author    Arthur van Hoff
 * @version     1.39, 03/18/98
 * @see     java.io.ByteArrayOutputStream
 * @see     java.lang.String
 * @since   JDK1.0
 */

public final class StringBuffer implements java.io.Serializable {
    /** The value is used for character storage. */
    private char value[];

    /** The count is the number of characters in the buffer. */
    private int count;

    /** A flag indicating whether the buffer is shared */
    private boolean shared;

    /** use serialVersionUID from JDK 1.0.2 for interoperability */
    static final long serialVersionUID = 3388685877147921107L;

    /**
     * Constructs a string buffer with no characters in it and an
     * initial capacity of 16 characters.
     */
    public StringBuffer() {
    this(16);
    }

    /**
     * Constructs a string buffer with no characters in it and an
     * initial capacity specified by the <code>length</code> argument.
     *
     * @param      length   the initial capacity.
     * @exception  NegativeArraySizeException  if the <code>length</code>
     *               argument is less than <code>0</code>.
     */
    public StringBuffer(int length) {
    value = new char[length];
    shared = false;
    }

    /**
     * Constructs a string buffer so that it represents the same
     * sequence of characters as the string argument. The initial
     * capacity of the string buffer is <code>16</code> plus the length
     * of the string argument.
     *
     * @param   str   the initial contents of the buffer.
     */
    public StringBuffer(String str) {
    this(str.length() + 16);
    append(str);
    }

    /**
     * Returns the length (character count) of this string buffer.
     *
     * @return  the number of characters in this string buffer.
     */
    public int length() {
    return count;
    }

    /**
     * Returns the current capacity of the String buffer. The capacity
     * is the amount of storage available for newly inserted
     * characters; beyond which an allocation will occur.
     *
     * @return  the current capacity of this string buffer.
     */
    public int capacity() {
    return value.length;
    }

    /**
     * Copies the buffer value.  This is normally only called when shared
     * is true.  It should only be called from a synchronized method.
     */
    private final void copy() {
    char newValue[] = new char[value.length];
    System.arraycopy(value, 0, newValue, 0, count);
    value = newValue;
    shared = false;
    }

    /**
     * Ensures that the capacity of the buffer is at least equal to the
     * specified minimum.
     * If the current capacity of this string buffer is less than the
     * argument, then a new internal buffer is allocated with greater
     * capacity. The new capacity is the larger of:
     * <ul>
     * <li>The <code>minimumCapacity</code> argument.
     * <li>Twice the old capacity, plus <code>2</code>.
     * </ul>
     * If the <code>minimumCapacity</code> argument is nonpositive, this
     * method takes no action and simply returns.
     *
     * @param   minimumCapacity   the minimum desired capacity.
     */
    public synchronized void ensureCapacity(int minimumCapacity) {
    if (minimumCapacity > value.length) {
        expandCapacity(minimumCapacity);
    }
    }

    /**
     * This implements the expansion semantics of ensureCapacity but is
     * unsynchronized for use internally by methods which are already
     * synchronized.
     *
     * @see java.lang.StringBuffer#ensureCapacity(int)
     */
    private void expandCapacity(int minimumCapacity) {
    int newCapacity = (value.length + 1) * 2;
    if (minimumCapacity > newCapacity) {
        newCapacity = minimumCapacity;
    }

    char newValue[] = new char[newCapacity];
    System.arraycopy(value, 0, newValue, 0, count);
    value = newValue;
    shared = false;
    }

    /**
     * Sets the length of this String buffer.
     * If the <code>newLength</code> argument is less than the current
     * length of the string buffer, the string buffer is truncated to
     * contain exactly the number of characters given by the
     * <code>newLength</code> argument.
     * <p>
     * If the <code>newLength</code> argument is greater than or equal
     * to the current length, sufficient null characters
     * (<code>'\u0000'</code>) are appended to the string buffer so that
     * length becomes the <code>newLength</code> argument.
     * <p>
     * The <code>newLength</code> argument must be greater than or equal
     * to <code>0</code>.
     *
     * @param      newLength   the new length of the buffer.
     * @exception  StringIndexOutOfBoundsException  if the
     *               <code>newLength</code> argument is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized void setLength(int newLength) {
    if (newLength < 0) {
        throw new StringIndexOutOfBoundsException(newLength);
    }

    if (newLength > value.length) {
        expandCapacity(newLength);
    }

    if (count < newLength) {
        if (shared) copy();
        for (; count < newLength; count++) {
        value[count] = '\0';
        }
    } else {
            count = newLength;
            if (shared) copy();
        }
    }

    /**
     * Returns the character at a specific index in this string buffer.
     * <p>
     * The first character of a string buffer is at index
     * <code>0</code>, the next at index <code>1</code>, and so on, for
     * array indexing.
     * <p>
     * The index argument must be greater than or equal to
     * <code>0</code>, and less than the length of this string buffer.
     *
     * @param      index   the index of the desired character.
     * @return     the character at the specified index of this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the index is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized char charAt(int index) {
    if ((index < 0) || (index >= count)) {
        throw new StringIndexOutOfBoundsException(index);
    }
    return value[index];
    }

    /**
     * Characters are copied from this string buffer into the
     * destination character array <code>dst</code>. The first character to
     * be copied is at index <code>srcBegin</code>; the last character to
     * be copied is at index <code>srcEnd-1.</code> The total number of
     * characters to be copied is <code>srcEnd-srcBegin</code>. The
     * characters are copied into the subarray of <code>dst</code> starting
     * at index <code>dstBegin</code> and ending at index:
     * <p><blockquote><pre>
     *     dstbegin + (srcEnd-srcBegin) - 1
     * </pre></blockquote>
     *
     * @param      srcBegin   start copying at this offset in the string buffer.
     * @param      srcEnd     stop copying at this offset in the string buffer.
     * @param      dst        the array to copy the data into.
     * @param      dstBegin   offset into <code>dst</code>.
     * @exception  StringIndexOutOfBoundsException  if there is an invalid
     *               index into the buffer.
     */
    public synchronized void getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) {
    if ((srcBegin < 0) || (srcBegin >= count)) {
        throw new StringIndexOutOfBoundsException(srcBegin);
    }
    if ((srcEnd < 0) || (srcEnd > count)) {
        throw new StringIndexOutOfBoundsException(srcEnd);
    }
    if (srcBegin < srcEnd) {
        System.arraycopy(value, srcBegin, dst, dstBegin, srcEnd - srcBegin);
    } else {
        if (srcBegin > srcEnd) {
        throw new StringIndexOutOfBoundsException
            ("StringBuffer.getChars(): begin > end");
        }
        /* We do nothing when srcBegin == srcEnd. */
    }
    }

    /**
     * The character at the specified index of this string buffer is set
     * to <code>ch</code>.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than the length of this string buffer.
     *
     * @param      index   the index of the character to modify.
     * @param      ch      the new character.
     * @exception  StringIndexOutOfBoundsException  if the index is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized void setCharAt(int index, char ch) {
    if ((index < 0) || (index >= count)) {
        throw new StringIndexOutOfBoundsException(index);
    }
    if (shared) copy();
    value[index] = ch;
    }

    /**
     * Appends the string representation of the <code>Object</code>
     * argument to this string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   obj   an <code>Object</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(java.lang.Object)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public synchronized StringBuffer append(Object obj) {
    return append(String.valueOf(obj));
    }

    /**
     * Appends the string to this string buffer.
     * <p>
     * The characters of the <code>String</code> argument are appended, in
     * order, to the contents of this string buffer, increasing the
     * length of this string buffer by the length of the argument.
     *
     * @param   str   a string.
     * @return  this string buffer.
     */
    public synchronized StringBuffer append(String str) {
    if (str == null) {
        str = String.valueOf(str);
    }

    int len = str.length();
    int newcount = count + len;
    if (newcount > value.length)
        expandCapacity(newcount);
    str.getChars(0, len, value, count);
    count = newcount;
    return this;
    }

    /**
     * Appends the string representation of the <code>char</code> array
     * argument to this string buffer.
     * <p>
     * The characters of the array argument are appended, in order, to
     * the contents of this string buffer. The length of this string
     * buffer increases by the length of the argument.
     *
     * @param   str   the characters to be appended.
     * @return  this string buffer.
     */
    public synchronized StringBuffer append(char str[]) {
    int len = str.length;
    int newcount = count + len;
    if (newcount > value.length)
        expandCapacity(newcount);
    System.arraycopy(str, 0, value, count, len);
    count = newcount;
    return this;
    }

    /**
     * Appends the string representation of a subarray of the
     * <code>char</code> array argument to this string buffer.
     * <p>
     * Characters of the character array <code>str</code>, starting at
     * index <code>offset</code>, are appended, in order, to the contents
     * of this string buffer. The length of this string buffer increases
     * by the value of <code>len</code>.
     *
     * @param   str      the characters to be appended.
     * @param   offset   the index of the first character to append.
     * @param   len      the number of characters to append.
     * @return  this string buffer.
     */
    public synchronized StringBuffer append(char str[], int offset, int len) {
        int newcount = count + len;
    if (newcount > value.length)
        expandCapacity(newcount);
    System.arraycopy(str, offset, value, count, len);
    count = newcount;
    return this;
    }

    /**
     * Appends the string representation of the <code>boolean</code>
     * argument to the string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   b   a <code>boolean</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(boolean)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public StringBuffer append(boolean b) {
    return append(String.valueOf(b));
    }

    /**
     * Appends the string representation of the <code>char</code>
     * argument to this string buffer.
     * <p>
     * The argument is appended to the contents of this string buffer.
     * The length of this string buffer increases by <code>1</code>.
     *
     * @param   ch   a <code>char</code>.
     * @return  this string buffer.
     */
    public synchronized StringBuffer append(char c) {
        int newcount = count + 1;
    if (newcount > value.length)
        expandCapacity(newcount);
    value[count++] = c;
    return this;
    }

    /**
     * Appends the string representation of the <code>int</code>
     * argument to this string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   i   an <code>int</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(int)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public StringBuffer append(int i) {
    return append(String.valueOf(i));
    }

    /**
     * Appends the string representation of the <code>long</code>
     * argument to this string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   l   a <code>long</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(long)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public StringBuffer append(long l) {
    return append(String.valueOf(l));
    }

    /**
     * Appends the string representation of the <code>float</code>
     * argument to this string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   f   a <code>float</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(float)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public StringBuffer append(float f) {
    return append(String.valueOf(f));
    }

    /**
     * Appends the string representation of the <code>double</code>
     * argument to this string buffer.
     * <p>
     * The argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then appended to this string buffer.
     *
     * @param   d   a <code>double</code>.
     * @return  this string buffer.
     * @see     java.lang.String#valueOf(double)
     * @see     java.lang.StringBuffer#append(java.lang.String)
     */
    public StringBuffer append(double d) {
    return append(String.valueOf(d));
    }

    /**
     * Inserts the string representation of the <code>Object</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        an <code>Object</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(java.lang.Object)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, Object obj) {
    return insert(offset, String.valueOf(obj));
    }

    /**
     * Inserts the string into this string buffer.
     * <p>
     * The characters of the <code>String</code> argument are inserted, in
     * order, into this string buffer at the indicated offset. The length
     * of this string buffer is increased by the length of the argument.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      str      a string.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, String str) {
    if ((offset < 0) || (offset > count)) {
        throw new StringIndexOutOfBoundsException();
    }

    if (str == null) {
        str = String.valueOf(str);
    }
    int len = str.length();
    int newcount = count + len;
    if (newcount > value.length)
        expandCapacity(newcount);
    else if (shared)
        copy();
    System.arraycopy(value, offset, value, offset + len, count - offset);
    str.getChars(0, len, value, offset);
    count = newcount;
    return this;
    }

    /**
     * Inserts the string representation of the <code>char</code> array
     * argument into this string buffer.
     * <p>
     * The characters of the array argument are inserted into the
     * contents of this string buffer at the position indicated by
     * <code>offset</code>. The length of this string buffer increases by
     * the length of the argument.
     *
     * @param      offset   the offset.
     * @param      ch       a character array.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     */
    public synchronized StringBuffer insert(int offset, char str[]) {
    if ((offset < 0) || (offset > count)) {
        throw new StringIndexOutOfBoundsException();
    }
    int len = str.length;
    int newcount = count + len;
    if (newcount > value.length)
        expandCapacity(newcount);
    else if (shared)
        copy();
    System.arraycopy(value, offset, value, offset + len, count - offset);
    System.arraycopy(str, 0, value, offset, len);
    count = newcount;
    return this;
    }

    /**
     * Inserts the string representation of the <code>boolean</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        a <code>boolean</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(boolean)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, boolean b) {
    return insert(offset, String.valueOf(b));
    }

    /**
     * Inserts the string representation of the <code>char</code>
     * argument into this string buffer.
     * <p>
     * The second argument is inserted into the contents of this string
     * buffer at the position indicated by <code>offset</code>. The length
     * of this string buffer increases by one.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      ch       a <code>char</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.StringBuffer#length()
     */
    public synchronized StringBuffer insert(int offset, char c) {
    int newcount = count + 1;
    if (newcount > value.length)
        expandCapacity(newcount);
    else if (shared)
        copy();
    System.arraycopy(value, offset, value, offset + 1, count - offset);
    value[offset] = c;
    count = newcount;
    return this;
    }

    /**
     * Inserts the string representation of the second <code>int</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        an <code>int</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(int)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, int i) {
    return insert(offset, String.valueOf(i));
    }

    /**
     * Inserts the string representation of the <code>long</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        a <code>long</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(long)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, long l) {
    return insert(offset, String.valueOf(l));
    }

    /**
     * Inserts the string representation of the <code>float</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        a <code>float</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(float)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, float f) {
    return insert(offset, String.valueOf(f));
    }

    /**
     * Inserts the string representation of the <code>double</code>
     * argument into this string buffer.
     * <p>
     * The second argument is converted to a string as if by the method
     * <code>String.valueOf</code>, and the characters of that
     * string are then inserted into this string buffer at the indicated
     * offset.
     * <p>
     * The offset argument must be greater than or equal to
     * <code>0</code>, and less than or equal to the length of this
     * string buffer.
     *
     * @param      offset   the offset.
     * @param      b        a <code>double</code>.
     * @return     this string buffer.
     * @exception  StringIndexOutOfBoundsException  if the offset is invalid.
     * @see        java.lang.String#valueOf(double)
     * @see        java.lang.StringBuffer#insert(int, java.lang.String)
     * @see        java.lang.StringBuffer#length()
     */
    public StringBuffer insert(int offset, double d) {
    return insert(offset, String.valueOf(d));
    }

    /**
     * The character sequence contained in this string buffer is
     * replaced by the reverse of the sequence.
     *
     * @return  this string buffer.
     * @since   JDK1.0.2
     */
    public synchronized StringBuffer reverse() {
    if (shared) copy();
    int n = count - 1;
    for (int j = (n-1) >> 1; j >= 0; --j) {
        char temp = value[j];
        value[j] = value[n - j];
        value[n - j] = temp;
    }
    return this;
    }

    /**
     * Converts to a string representing the data in this string buffer.
     * A new <code>String</code> object is allocated and initialized to
     * contain the character sequence currently represented by this
     * string buffer. This <code>String</code> is then returned. Subsequent
     * changes to the string buffer do not affect the contents of the
     * <code>String</code>.
     *
     * @return  a string representation of the string buffer.
     */
    public String toString() {
    return new String(this);
    }

    //
    // The following two methods are needed by String to efficiently
    // convert a StringBuffer into a String.  They are not public.
    // They shouldn't be called by anyone but String.
    final void setShared() { shared = true; }
    final char[] getValue() { return value; }
}