* 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 * that is consistent with the order of the method calls made by each of * the individual threads involved. *
* String buffers are used by the compiler to implement the binary
* string concatenation operator +. For example, the code:
*
* x = "a" + 4 + "c" *
* is compiled to the equivalent of: *
* x = new StringBuffer().append("a").append(4).append("c")
* .toString()
*
* The principal operations on a StringBuffer are the
* append and insert 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
* append method always adds these characters at the end
* of the buffer; the insert method adds the characters at
* a specified point.
*
* For example, if z refers to a string buffer object
* whose current contents are "start", then
* the method call z.append("le") would cause the string
* buffer to contain "startle", whereas
* z.insert(4, "le") would alter the string buffer to
* contain "starlet".
*
* In general, if sb refers to an instance of a StringBuffer,
* then sb.append(x) has the same effect as
* sb.insert(sb.length(), x).
*
* 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 1.78, 05/16/03
* @see java.io.ByteArrayOutputStream
* @see java.lang.String
* @since JDK1.0
*/
public final class StringBuffer
implements java.io.Serializable, CharSequence
{
/**
* The value is used for character storage.
*
* @serial
*/
private char value[];
/**
* The count is the number of characters in the buffer.
*
* @serial
*/
private int count;
/**
* A flag indicating whether the buffer is shared
*
* @serial
*/
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 length argument.
*
* @param length the initial capacity.
* @exception NegativeArraySizeException if the length
* argument is less than 0.
*/
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; in other
* words, the initial contents of the string buffer is a copy of the
* argument string. The initial capacity of the string buffer is
* 16 plus the length of the string argument.
*
* @param str the initial contents of the buffer.
* @exception NullPointerException if str is null
*/
public StringBuffer(String str) {
this(str.length() + 16);
append(str);
}
/**
* Returns the length (character count) of this string buffer.
*
* @return the length of the sequence of characters currently
* represented by this string buffer.
*/
public synchronized 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 synchronized 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:
*
minimumCapacity argument.
* 2.
* minimumCapacity 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 (newCapacity < 0) {
newCapacity = Integer.MAX_VALUE;
} else 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.
* This string buffer is altered to represent a new character sequence
* whose length is specified by the argument. For every nonnegative
* index k less than newLength, the character at
* index k in the new character sequence is the same as the
* character at index k in the old sequence if k is less
* than the length of the old character sequence; otherwise, it is the
* null character '\u0000'.
*
* In other words, if the newLength 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
* newLength argument.
*
* If the newLength argument is greater than or equal
* to the current length, sufficient null characters
* ('\u0000') are appended to the string buffer so that
* length becomes the newLength argument.
*
* The newLength argument must be greater than or equal
* to 0.
*
* @param newLength the new length of the buffer.
* @exception IndexOutOfBoundsException if the
* newLength argument is negative.
* @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) {
if (newLength > 0) {
copy();
} else {
// If newLength is zero, assume the StringBuffer is being
// stripped for reuse; Make new buffer of default size
value = new char[16];
shared = false;
}
}
}
}
/**
* The specified character of the sequence currently represented by
* the string buffer, as indicated by the index argument,
* is returned. The first character of a string buffer is at index
* 0, the next at index 1, and so on, for
* array indexing.
*
* The index argument must be greater than or equal to
* 0, 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 IndexOutOfBoundsException if index is
* negative or greater than or equal to length().
* @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 dst. The first character to
* be copied is at index srcBegin; the last character to
* be copied is at index srcEnd-1. The total number of
* characters to be copied is srcEnd-srcBegin. The
* characters are copied into the subarray of dst starting
* at index dstBegin and ending at index:
*
* dstbegin + (srcEnd-srcBegin) - 1
* dst.
* @exception NullPointerException if dst is
* null.
* @exception IndexOutOfBoundsException if any of the following is true:
* srcBegin is negative
* dstBegin is negative
* srcBegin argument is greater than
* the srcEnd argument.
* srcEnd is greater than
* this.length(), the current length of this
* string buffer.
* dstBegin+srcEnd-srcBegin is greater than
* dst.length
* ch. The string buffer is altered to represent a new
* character sequence that is identical to the old character sequence,
* except that it contains the character ch at position
* index.
*
* The index argument must be greater than or equal to
* 0, and less than the length of this string buffer.
*
* @param index the index of the character to modify.
* @param ch the new character.
* @exception IndexOutOfBoundsException if index is
* negative or greater than or equal to length().
* @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 Object
* argument to this string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param obj an Object.
* @return a reference to this StringBuffer object.
* @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.
*
* The characters of the String 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.
* If str is null, then the four characters
* "null" are appended to this string buffer.
*
* Let n be the length of the old character sequence, the one
* contained in the string buffer just prior to execution of the
* append method. Then the character at index k in
* the new character sequence is equal to the character at index k
* in the old character sequence, if k is less than n;
* otherwise, it is equal to the character at index k-n in the
* argument str.
*
* @param str a string.
* @return a reference to this StringBuffer.
*/
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 specified StringBuffer to this
* StringBuffer.
*
* The characters of the StringBuffer argument are appended, * in order, to the contents of this StringBuffer, increasing the * length of this StringBuffer by the length of the argument. * If sb is null, then the four characters * "null" are appended to this StringBuffer. *
* Let n be the length of the old character sequence, the one
* contained in the StringBuffer just prior to execution of the
* append method. Then the character at index k in
* the new character sequence is equal to the character at index k
* in the old character sequence, if k is less than n;
* otherwise, it is equal to the character at index k-n in the
* argument sb.
*
* The method ensureCapacity is first called on this
* StringBuffer with the new buffer length as its argument.
* (This ensures that the storage of this StringBuffer is
* adequate to contain the additional characters being appended.)
*
* @param sb the StringBuffer to append.
* @return a reference to this StringBuffer.
* @since 1.4
*/
public synchronized StringBuffer append(StringBuffer sb) {
if (sb == null) {
sb = NULL;
}
int len = sb.length();
int newcount = count + len;
if (newcount > value.length)
expandCapacity(newcount);
sb.getChars(0, len, value, count);
count = newcount;
return this;
}
private static final StringBuffer NULL = new StringBuffer("null");
/**
* Appends the string representation of the char array
* argument to this string buffer.
*
* 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. *
* The overall effect is exactly as if the argument were converted to
* a string by the method {@link String#valueOf(char[])} and the
* characters of that string were then {@link #append(String) appended}
* to this StringBuffer object.
*
* @param str the characters to be appended.
* @return a reference to this StringBuffer object.
*/
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
* char array argument to this string buffer.
*
* Characters of the character array str, starting at
* index offset, are appended, in order, to the contents
* of this string buffer. The length of this string buffer increases
* by the value of len.
*
* The overall effect is exactly as if the arguments were converted to
* a string by the method {@link String#valueOf(char[],int,int)} and the
* characters of that string were then {@link #append(String) appended}
* to this StringBuffer object.
*
* @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 a reference to this StringBuffer object.
*/
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 boolean
* argument to the string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param b a boolean.
* @return a reference to this StringBuffer.
* @see java.lang.String#valueOf(boolean)
* @see java.lang.StringBuffer#append(java.lang.String)
*/
public synchronized StringBuffer append(boolean b) {
if (b) {
int newcount = count + 4;
if (newcount > value.length)
expandCapacity(newcount);
value[count++] = 't';
value[count++] = 'r';
value[count++] = 'u';
value[count++] = 'e';
} else {
int newcount = count + 5;
if (newcount > value.length)
expandCapacity(newcount);
value[count++] = 'f';
value[count++] = 'a';
value[count++] = 'l';
value[count++] = 's';
value[count++] = 'e';
}
return this;
}
/**
* Appends the string representation of the char
* argument to this string buffer.
*
* The argument is appended to the contents of this string buffer.
* The length of this string buffer increases by 1.
*
* The overall effect is exactly as if the argument were converted to
* a string by the method {@link String#valueOf(char)} and the character
* in that string were then {@link #append(String) appended} to this
* StringBuffer object.
*
* @param c a char.
* @return a reference to this StringBuffer object.
*/
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 int
* argument to this string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param i an int.
* @return a reference to this StringBuffer object.
* @see java.lang.String#valueOf(int)
* @see java.lang.StringBuffer#append(java.lang.String)
*/
public synchronized StringBuffer append(int i) {
Integer.appendTo(i, this);
return this;
}
/**
* Appends the string representation of the long
* argument to this string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param l a long.
* @return a reference to this StringBuffer object.
* @see java.lang.String#valueOf(long)
* @see java.lang.StringBuffer#append(java.lang.String)
*/
public synchronized StringBuffer append(long l) {
Long.appendTo(l, this);
return this;
}
/**
* Appends the string representation of the float
* argument to this string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param f a float.
* @return a reference to this StringBuffer object.
* @see java.lang.String#valueOf(float)
* @see java.lang.StringBuffer#append(java.lang.String)
*/
public synchronized StringBuffer append(float f) {
new FloatingDecimal(f).appendTo(this);
return this;
}
/**
* Appends the string representation of the double
* argument to this string buffer.
*
* The argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then appended to this string buffer.
*
* @param d a double.
* @return a reference to this StringBuffer object.
* @see java.lang.String#valueOf(double)
* @see java.lang.StringBuffer#append(java.lang.String)
*/
public synchronized StringBuffer append(double d) {
new FloatingDecimal(d).appendTo(this);
return this;
}
/**
* Removes the characters in a substring of this StringBuffer.
* The substring begins at the specified start and extends to
* the character at index end - 1 or to the end of the
* StringBuffer if no such character exists. If
* start is equal to end, no changes are made.
*
* @param start The beginning index, inclusive.
* @param end The ending index, exclusive.
* @return This string buffer.
* @exception StringIndexOutOfBoundsException if start
* is negative, greater than length(), or
* greater than end.
* @since 1.2
*/
public synchronized StringBuffer delete(int start, int end) {
if (start < 0)
throw new StringIndexOutOfBoundsException(start);
if (end > count)
end = count;
if (start > end)
throw new StringIndexOutOfBoundsException();
int len = end - start;
if (len > 0) {
if (shared)
copy();
System.arraycopy(value, start+len, value, start, count-end);
count -= len;
}
return this;
}
/**
* Removes the character at the specified position in this
* StringBuffer (shortening the StringBuffer
* by one character).
*
* @param index Index of character to remove
* @return This string buffer.
* @exception StringIndexOutOfBoundsException if the index
* is negative or greater than or equal to
* length().
* @since 1.2
*/
public synchronized StringBuffer deleteCharAt(int index) {
if ((index < 0) || (index >= count))
throw new StringIndexOutOfBoundsException();
if (shared)
copy();
System.arraycopy(value, index+1, value, index, count-index-1);
count--;
return this;
}
/**
* Replaces the characters in a substring of this StringBuffer
* with characters in the specified String. The substring
* begins at the specified start and extends to the character
* at index end - 1 or to the end of the
* StringBuffer if no such character exists. First the
* characters in the substring are removed and then the specified
* String is inserted at start. (The
* StringBuffer will be lengthened to accommodate the
* specified String if necessary.)
*
* @param start The beginning index, inclusive.
* @param end The ending index, exclusive.
* @param str String that will replace previous contents.
* @return This string buffer.
* @exception StringIndexOutOfBoundsException if start
* is negative, greater than length(), or
* greater than end.
* @since 1.2
*/
public synchronized StringBuffer replace(int start, int end, String str) {
if (start < 0)
throw new StringIndexOutOfBoundsException(start);
if (end > count)
end = count;
if (start > end)
throw new StringIndexOutOfBoundsException();
int len = str.length();
int newCount = count + len - (end - start);
if (newCount > value.length)
expandCapacity(newCount);
else if (shared)
copy();
System.arraycopy(value, end, value, start + len, count - end);
str.getChars(0, len, value, start);
count = newCount;
return this;
}
/**
* Returns a new String that contains a subsequence of
* characters currently contained in this StringBuffer.The
* substring begins at the specified index and extends to the end of the
* StringBuffer.
*
* @param start The beginning index, inclusive.
* @return The new string.
* @exception StringIndexOutOfBoundsException if start is
* less than zero, or greater than the length of this
* StringBuffer.
* @since 1.2
*/
public synchronized String substring(int start) {
return substring(start, count);
}
/**
* Returns a new character sequence that is a subsequence of this sequence.
*
*
An invocation of this method of the form * *
* sb.subSequence(begin, end)
* sb.substring(begin, end)String that contains a subsequence of
* characters currently contained in this StringBuffer. The
* substring begins at the specified start and
* extends to the character at index end - 1. An
* exception is thrown if
*
* @param start The beginning index, inclusive.
* @param end The ending index, exclusive.
* @return The new string.
* @exception StringIndexOutOfBoundsException if start
* or end are negative or greater than
* length(), or start is
* greater than end.
* @since 1.2
*/
public synchronized String substring(int start, int end) {
if (start < 0)
throw new StringIndexOutOfBoundsException(start);
if (end > count)
throw new StringIndexOutOfBoundsException(end);
if (start > end)
throw new StringIndexOutOfBoundsException(end - start);
return new String(value, start, end - start);
}
/**
* Inserts the string representation of a subarray of the str
* array argument into this string buffer. The subarray begins at the
* specified offset and extends len characters.
* The characters of the subarray are inserted into this string buffer at
* the position indicated by index. The length of this
* StringBuffer increases by len characters.
*
* @param index position at which to insert subarray.
* @param str A character array.
* @param offset the index of the first character in subarray to
* to be inserted.
* @param len the number of characters in the subarray to
* to be inserted.
* @return This string buffer.
* @exception StringIndexOutOfBoundsException if index
* is negative or greater than length(), or
* offset or len are negative, or
* (offset+len) is greater than
* str.length.
* @since 1.2
*/
public synchronized StringBuffer insert(int index, char str[], int offset,
int len) {
if ((index < 0) || (index > count))
throw new StringIndexOutOfBoundsException();
if ((offset < 0) || (offset + len < 0) || (offset + len > str.length))
throw new StringIndexOutOfBoundsException(offset);
if (len < 0)
throw new StringIndexOutOfBoundsException(len);
int newCount = count + len;
if (newCount > value.length)
expandCapacity(newCount);
else if (shared)
copy();
System.arraycopy(value, index, value, index + len, count - index);
System.arraycopy(str, offset, value, index, len);
count = newCount;
return this;
}
/**
* Inserts the string representation of the Object
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the indicated
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param obj an Object.
* @return a reference to this StringBuffer object.
* @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.
*
* The characters of the String argument are inserted, in
* order, into this string buffer at the indicated offset, moving up any
* characters originally above that position and increasing the length
* of this string buffer by the length of the argument. If
* str is null, then the four characters
* "null" are inserted into this string buffer.
*
* The character at index k in the new character sequence is * equal to: *
offset
* -offset in the
* argument str, if k is not less than
* offset but is less than offset+str.length()
* -str.length() in the
* old character sequence, if k is not less than
* offset+str.length()
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param str a string.
* @return a reference to this StringBuffer object.
* @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 char array
* argument into this string buffer.
*
* The characters of the array argument are inserted into the
* contents of this string buffer at the position indicated by
* offset. The length of this string buffer increases by
* the length of the argument.
*
* The overall effect is exactly as if the argument were converted to
* a string by the method {@link String#valueOf(char[])} and the
* characters of that string were then
* {@link #insert(int,String) inserted} into this
* StringBuffer object at the position indicated by
* offset.
*
* @param offset the offset.
* @param str a character array.
* @return a reference to this StringBuffer object.
* @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 boolean
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the indicated
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param b a boolean.
* @return a reference to this StringBuffer object.
* @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 char
* argument into this string buffer.
*
* The second argument is inserted into the contents of this string
* buffer at the position indicated by offset. The length
* of this string buffer increases by one.
*
* The overall effect is exactly as if the argument were converted to
* a string by the method {@link String#valueOf(char)} and the character
* in that string were then {@link #insert(int, String) inserted} into
* this StringBuffer object at the position indicated by
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param c a char.
* @return a reference to this StringBuffer object.
* @exception IndexOutOfBoundsException 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 int
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the indicated
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param i an int.
* @return a reference to this StringBuffer object.
* @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 long
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the position
* indicated by offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param l a long.
* @return a reference to this StringBuffer object.
* @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 float
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the indicated
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param f a float.
* @return a reference to this StringBuffer object.
* @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 double
* argument into this string buffer.
*
* The second argument is converted to a string as if by the method
* String.valueOf, and the characters of that
* string are then inserted into this string buffer at the indicated
* offset.
*
* The offset argument must be greater than or equal to
* 0, and less than or equal to the length of this
* string buffer.
*
* @param offset the offset.
* @param d a double.
* @return a reference to this StringBuffer object.
* @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));
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring. The integer returned is the smallest value
* k such that:
*
* this.toString().startsWith(str, k)
* true.
*
* @param str any string.
* @return if the string argument occurs as a substring within this
* object, then the index of the first character of the first
* such substring is returned; if it does not occur as a
* substring, -1 is returned.
* @exception java.lang.NullPointerException if str is
* null.
* @since 1.4
*/
public int indexOf(String str) {
return indexOf(str, 0);
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring, starting at the specified index. The integer
* returned is the smallest value k for which:
*
* k >= Math.min(fromIndex, str.length()) &&
* this.toString().startsWith(str, k)
* str is
* null.
* @since 1.4
*/
public synchronized int indexOf(String str, int fromIndex) {
return String.indexOf(value, 0, count,
str.toCharArray(), 0, str.length(), fromIndex);
}
/**
* Returns the index within this string of the rightmost occurrence
* of the specified substring. The rightmost empty string "" is
* considered to occur at the index value this.length().
* The returned index is the largest value k such that
*
* this.toString().startsWith(str, k)
* -1 is returned.
* @exception java.lang.NullPointerException if str is
* null.
* @since 1.4
*/
public synchronized int lastIndexOf(String str) {
return lastIndexOf(str, count);
}
/**
* Returns the index within this string of the last occurrence of the
* specified substring. The integer returned is the largest value k
* such that:
*
* k <= Math.min(fromIndex, str.length()) &&
* this.toString().startsWith(str, k)
* str is
* null.
* @since 1.4
*/
public synchronized int lastIndexOf(String str, int fromIndex) {
return String.lastIndexOf(value, 0, count,
str.toCharArray(), 0, str.length(), fromIndex);
}
/**
* The character sequence contained in this string buffer is
* replaced by the reverse of the sequence.
*
* Let n be the length of the old character sequence, the one
* contained in the string buffer just prior to execution of the
* reverse method. Then the character at index k in
* the new character sequence is equal to the character at index
* n-k-1 in the old character sequence.
*
* @return a reference to this StringBuffer object.
* @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 String object is allocated and initialized to
* contain the character sequence currently represented by this
* string buffer. This String is then returned. Subsequent
* changes to the string buffer do not affect the contents of the
* String.
*
* Implementation advice: This method can be coded so as to create a new
* String object without allocating new memory to hold a
* copy of the character sequence. Instead, the string can share the
* memory used by the string buffer. Any subsequent operation that alters
* the content or capacity of the string buffer must then make a copy of
* the internal buffer at that time. This strategy is effective for
* reducing the amount of memory allocated by a string concatenation
* operation when it is implemented using a string buffer.
*
* @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; }
/**
* readObject is called to restore the state of the StringBuffer from
* a stream.
*/
private synchronized void readObject(java.io.ObjectInputStream s)
throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
value = (char[]) value.clone();
shared = false;
}
}