+ * 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. + *
+ * 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).
+ *
+ * Whenever an operation occurs involving a source sequence (such as + * appending or inserting from a source sequence) this class synchronizes + * only on the string buffer performing the operation, not on the source. + *
+ * 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.
+ *
+ * As of release JDK 5, this class has been supplemented with an equivalent
+ * class designed for use by a single thread, {@link StringBuilder}. The
+ * StringBuilder class should generally be used in preference to
+ * this one, as it supports all of the same operations but it is faster, as
+ * it performs no synchronization.
+ *
+ * @author Arthur van Hoff
+ * @see java.lang.StringBuilder
+ * @see java.lang.String
+ * @since JDK1.0
+ */
+ public final class StringBuffer
+ extends AbstractStringBuilder
+ implements java.io.Serializable, CharSequence
+{
+
+ /** 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() {
+ super(16);
+ }
+
+ /**
+ * Constructs a string buffer with no characters in it and
+ * the specified initial capacity.
+ *
+ * @param capacity the initial capacity.
+ * @exception NegativeArraySizeException if the capacity
+ * argument is less than 0.
+ */
+ public StringBuffer(int capacity) {
+ super(capacity);
+ }
+
+ /**
+ * Constructs a string buffer initialized to the contents of the
+ * specified 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) {
+ super(str.length() + 16);
+ append(str);
+ }
+
+ /**
+ * Constructs a string buffer that contains the same characters
+ * as the specified CharSequence. The initial capacity of
+ * the string buffer is 16 plus the length of the
+ * CharSequence argument.
+ *
+ * If the length of the specified CharSequence is
+ * less than or equal to zero, then an empty buffer of capacity
+ * 16 is returned.
+ *
+ * @param seq the sequence to copy.
+ * @exception NullPointerException if seq is null
+ * @since 1.5
+ */
+ public StringBuffer(CharSequence seq) {
+ this(seq.length() + 16);
+ append(seq);
+ }
+
+ public synchronized int length() {
+ return count;
+ }
+
+ public synchronized int capacity() {
+ return value.length;
+ }
+
+
+ public synchronized void ensureCapacity(int minimumCapacity) {
+ if (minimumCapacity > value.length) {
+ expandCapacity(minimumCapacity);
+ }
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized void trimToSize() {
+ super.trimToSize();
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @see #length()
+ */
+ public synchronized void setLength(int newLength) {
+ super.setLength(newLength);
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @see #length()
+ */
+ public synchronized char charAt(int index) {
+ if ((index < 0) || (index >= count))
+ throw new StringIndexOutOfBoundsException(index);
+ return value[index];
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized int codePointAt(int index) {
+ return super.codePointAt(index);
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized int codePointBefore(int index) {
+ return super.codePointBefore(index);
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized int codePointCount(int beginIndex, int endIndex) {
+ return super.codePointCount(beginIndex, endIndex);
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized int offsetByCodePoints(int index, int codePointOffset) {
+ return super.offsetByCodePoints(index, codePointOffset);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
+ int dstBegin)
+ {
+ super.getChars(srcBegin, srcEnd, dst, dstBegin);
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @see #length()
+ */
+ public synchronized void setCharAt(int index, char ch) {
+ if ((index < 0) || (index >= count))
+ throw new StringIndexOutOfBoundsException(index);
+ value[index] = ch;
+ }
+
+ public synchronized StringBuffer append(Object obj) {
+ super.append(String.valueOf(obj));
+ return this;
+ }
+
+ public synchronized StringBuffer append(String str) {
+ super.append(str);
+ return this;
+ }
+
+ /**
+ * Appends the specified StringBuffer to this sequence.
+ *
+ * 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.
+ *
+ * This method synchronizes on this (the destination)
+ * object but does not synchronize on the source (sb).
+ *
+ * @param sb the StringBuffer to append.
+ * @return a reference to this object.
+ * @since 1.4
+ */
+ public synchronized StringBuffer append(StringBuffer sb) {
+ super.append(sb);
+ return this;
+ }
+
+
+ /**
+ * Appends the specified CharSequence to this
+ * sequence.
+ *
+ * The characters of the CharSequence argument are appended,
+ * in order, increasing the length of this sequence by the length of the
+ * argument.
+ *
+ *
The result of this method is exactly the same as if it were an + * invocation of this.append(s, 0, s.length()); + * + *
This method synchronizes on this (the destination)
+ * object but does not synchronize on the source (s).
+ *
+ *
If s is null, then the four characters
+ * "null" are appended.
+ *
+ * @param s the CharSequence to append.
+ * @return a reference to this object.
+ * @since 1.5
+ */
+ public StringBuffer append(CharSequence s) {
+ // Note, synchronization achieved via other invocations
+ if (s == null)
+ s = "null";
+ if (s instanceof String)
+ return this.append((String)s);
+ if (s instanceof StringBuffer)
+ return this.append((StringBuffer)s);
+ return this.append(s, 0, s.length());
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @since 1.5
+ */
+ public synchronized StringBuffer append(CharSequence s, int start, int end)
+ {
+ super.append(s, start, end);
+ return this;
+ }
+
+ public synchronized StringBuffer append(char[] str) {
+ super.append(str);
+ return this;
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized StringBuffer append(char[] str, int offset, int len) {
+ super.append(str, offset, len);
+ return this;
+ }
+
+ public synchronized StringBuffer append(boolean b) {
+ super.append(b);
+ return this;
+ }
+
+ public synchronized StringBuffer append(char c) {
+ super.append(c);
+ return this;
+ }
+
+ public synchronized StringBuffer append(int i) {
+ super.append(i);
+ return this;
+ }
+
+ /**
+ * @since 1.5
+ */
+ public synchronized StringBuffer appendCodePoint(int codePoint) {
+ super.appendCodePoint(codePoint);
+ return this;
+ }
+
+ public synchronized StringBuffer append(long lng) {
+ super.append(lng);
+ return this;
+ }
+
+ public synchronized StringBuffer append(float f) {
+ super.append(f);
+ return this;
+ }
+
+ public synchronized StringBuffer append(double d) {
+ super.append(d);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized StringBuffer delete(int start, int end) {
+ super.delete(start, end);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized StringBuffer deleteCharAt(int index) {
+ super.deleteCharAt(index);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized StringBuffer replace(int start, int end, String str) {
+ super.replace(start, end, str);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized String substring(int start) {
+ return substring(start, count);
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @since 1.4
+ */
+ public synchronized CharSequence subSequence(int start, int end) {
+ return super.substring(start, end);
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized String substring(int start, int end) {
+ return super.substring(start, end);
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ * @since 1.2
+ */
+ public synchronized StringBuffer insert(int index, char[] str, int offset,
+ int len)
+ {
+ super.insert(index, str, offset, len);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized StringBuffer insert(int offset, Object obj) {
+ super.insert(offset, String.valueOf(obj));
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized StringBuffer insert(int offset, String str) {
+ super.insert(offset, str);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized StringBuffer insert(int offset, char[] str) {
+ super.insert(offset, str);
+ return this;
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @since 1.5
+ */
+ public StringBuffer insert(int dstOffset, CharSequence s) {
+ // Note, synchronization achieved via other invocations
+ if (s == null)
+ s = "null";
+ if (s instanceof String)
+ return this.insert(dstOffset, (String)s);
+ return this.insert(dstOffset, s, 0, s.length());
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ * @since 1.5
+ */
+ public synchronized StringBuffer insert(int dstOffset, CharSequence s,
+ int start, int end)
+ {
+ super.insert(dstOffset, s, start, end);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public StringBuffer insert(int offset, boolean b) {
+ return insert(offset, String.valueOf(b));
+ }
+
+ /**
+ * @throws IndexOutOfBoundsException {@inheritDoc}
+ */
+ public synchronized StringBuffer insert(int offset, char c) {
+ super.insert(offset, c);
+ return this;
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public StringBuffer insert(int offset, int i) {
+ return insert(offset, String.valueOf(i));
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public StringBuffer insert(int offset, long l) {
+ return insert(offset, String.valueOf(l));
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public StringBuffer insert(int offset, float f) {
+ return insert(offset, String.valueOf(f));
+ }
+
+ /**
+ * @throws StringIndexOutOfBoundsException {@inheritDoc}
+ */
+ public StringBuffer insert(int offset, double d) {
+ return insert(offset, String.valueOf(d));
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @since 1.4
+ */
+ public int indexOf(String str) {
+ return indexOf(str, 0);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @since 1.4
+ */
+ public synchronized int indexOf(String str, int fromIndex) {
+ return super.indexOf(str, fromIndex);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @since 1.4
+ */
+ public int lastIndexOf(String str) {
+ // Note, synchronization achieved via other invocations
+ return lastIndexOf(str, count);
+ }
+
+ /**
+ * @throws NullPointerException {@inheritDoc}
+ * @since 1.4
+ */
+ public synchronized int lastIndexOf(String str, int fromIndex) {
+ return String.lastIndexOf(value, 0, count,
+ str.toCharArray(), 0, str.length(), fromIndex);
+ }
+
+ /**
+ * @since JDK1.0.2
+ */
+ public synchronized StringBuffer reverse() {
+ super.reverse();
+ return this;
+ }
+
+ public synchronized String toString() {
+ return new String(value, 0, count);
+ }
+
+// /**
+// * Serializable fields for StringBuffer.
+// *
+// * @serialField value char[]
+// * The backing character array of this StringBuffer.
+// * @serialField count int
+// * The number of characters in this StringBuffer.
+// * @serialField shared boolean
+// * A flag indicating whether the backing array is shared.
+// * The value is ignored upon deserialization.
+// */
+// private static final java.io.ObjectStreamField[] serialPersistentFields =
+// {
+// new java.io.ObjectStreamField("value", char[].class),
+// new java.io.ObjectStreamField("count", Integer.TYPE),
+// new java.io.ObjectStreamField("shared", Boolean.TYPE),
+// };
+//
+// /**
+// * readObject is called to restore the state of the StringBuffer from
+// * a stream.
+// */
+// private synchronized void writeObject(java.io.ObjectOutputStream s)
+// throws java.io.IOException {
+// java.io.ObjectOutputStream.PutField fields = s.putFields();
+// fields.put("value", value);
+// fields.put("count", count);
+// fields.put("shared", false);
+// s.writeFields();
+// }
+//
+// /**
+// * readObject is called to restore the state of the StringBuffer from
+// * a stream.
+// */
+// private void readObject(java.io.ObjectInputStream s)
+// throws java.io.IOException, ClassNotFoundException {
+// java.io.ObjectInputStream.GetField fields = s.readFields();
+// value = (char[])fields.get("value", null);
+// count = fields.get("count", 0);
+// }
+}