* 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 {@code StringBuffer} are the * {@code append} and {@code 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 * {@code append} method always adds these characters at the end * of the buffer; the {@code insert} method adds the characters at * a specified point. *
* For example, if {@code z} refers to a string buffer object * whose current contents are {@code "start"}, then * the method call {@code z.append("le")} would cause the string * buffer to contain {@code "startle"}, whereas * {@code z.insert(4, "le")} would alter the string buffer to * contain {@code "starlet"}. *
* In general, if sb refers to an instance of a {@code StringBuffer}, * then {@code sb.append(x)} has the same effect as * {@code 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. * Note that while {@code StringBuffer} is designed to be safe to use * concurrently from multiple threads, if the constructor or the * {@code append} or {@code insert} operation is passed a source sequence * that is shared across threads, the calling code must ensure * that the operation has a consistent and unchanging view of the source * sequence for the duration of the operation. * This could be satisfied by the caller holding a lock during the * operation's call, by using an immutable source sequence, or by not * sharing the source sequence across threads. *
* 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. *
* Unless otherwise noted, passing a {@code null} argument to a constructor * or method in this class will cause a {@link NullPointerException} to be * thrown. *
* As of release JDK 5, this class has been supplemented with an equivalent
* class designed for use by a single thread, {@link StringBuilder}. The
* {@code 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.
*
* @apiNote
* {@code StringBuffer} implements {@code Comparable} but does not override
* {@link Object#equals equals}. Thus, the natural ordering of {@code StringBuffer}
* is inconsistent with equals. Care should be exercised if {@code StringBuffer}
* objects are used as keys in a {@code SortedMap} or elements in a {@code SortedSet}.
* See {@link Comparable}, {@link java.util.SortedMap SortedMap}, or
* {@link java.util.SortedSet SortedSet} for more information.
*
* @author Arthur van Hoff
* @see java.lang.StringBuilder
* @see java.lang.String
* @since 1.0
*/
public final class StringBuffer
extends AbstractStringBuilder
implements java.io.Serializable, Comparable
* If the length of the specified {@code CharSequence} is
* less than or equal to zero, then an empty buffer of capacity
* {@code 16} is returned.
*
* @param seq the sequence to copy.
* @since 1.5
*/
public StringBuffer(CharSequence seq) {
this(seq.length() + 16);
append(seq);
}
/**
* Compares two {@code StringBuffer} instances lexicographically. This method
* follows the same rules for lexicographical comparison as defined in the
* {@linkplain java.lang.CharSequence#compare(java.lang.CharSequence,
* java.lang.CharSequence) CharSequence.compare(this, another)} method.
*
*
* For finer-grained, locale-sensitive String comparison, refer to
* {@link java.text.Collator}.
*
* @implNote
* This method synchronizes on {@code this}, the current object, but not
* {@code StringBuffer another} with which {@code this StringBuffer} is compared.
*
* @param another the {@code StringBuffer} to be compared with
*
* @return the value {@code 0} if this {@code StringBuffer} contains the same
* character sequence as that of the argument {@code StringBuffer}; a negative integer
* if this {@code StringBuffer} is lexicographically less than the
* {@code StringBuffer} argument; or a positive integer if this {@code StringBuffer}
* is lexicographically greater than the {@code StringBuffer} argument.
*
* @since 11
*/
@Override
public synchronized int compareTo(StringBuffer another) {
return super.compareTo(another);
}
@Override
// We don't want to inline this method to be able to perform String-related
// optimizations with intrinsics.
@NeverInline
public synchronized int length() {
return count;
}
@Override
public synchronized int capacity() {
return super.capacity();
}
@Override
public synchronized void ensureCapacity(int minimumCapacity) {
super.ensureCapacity(minimumCapacity);
}
/**
* @since 1.5
*/
@Override
public synchronized void trimToSize() {
super.trimToSize();
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @see #length()
*/
@Override
public synchronized void setLength(int newLength) {
toStringCache = null;
super.setLength(newLength);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @see #length()
*/
@Override
public synchronized char charAt(int index) {
return super.charAt(index);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized int codePointAt(int index) {
return super.codePointAt(index);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized int codePointBefore(int index) {
return super.codePointBefore(index);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized int codePointCount(int beginIndex, int endIndex) {
return super.codePointCount(beginIndex, endIndex);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized int offsetByCodePoints(int index, int codePointOffset) {
return super.offsetByCodePoints(index, codePointOffset);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized void getChars(int srcBegin, int srcEnd, char[] dst,
int dstBegin)
{
super.getChars(srcBegin, srcEnd, dst, dstBegin);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @see #length()
*/
@Override
public synchronized void setCharAt(int index, char ch) {
toStringCache = null;
super.setCharAt(index, ch);
}
@Override
public synchronized StringBuffer append(Object obj) {
toStringCache = null;
super.append(String.valueOf(obj));
return this;
}
@Override
@HotSpotIntrinsicCandidate
// We don't want to inline this method to be able to perform String-related
// optimizations with intrinsics.
@NeverInline
public synchronized StringBuffer append(String str) {
toStringCache = null;
super.append(str);
return this;
}
/**
* Appends the specified {@code StringBuffer} to this sequence.
*
* The characters of the {@code StringBuffer} argument are appended,
* in order, to the contents of this {@code StringBuffer}, increasing the
* length of this {@code StringBuffer} by the length of the argument.
* If {@code sb} is {@code null}, then the four characters
* {@code "null"} are appended to this {@code StringBuffer}.
*
* Let n be the length of the old character sequence, the one
* contained in the {@code StringBuffer} just prior to execution of the
* {@code 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 {@code sb}.
*
* This method synchronizes on {@code this}, the destination
* object, but does not synchronize on the source ({@code sb}).
*
* @param sb the {@code StringBuffer} to append.
* @return a reference to this object.
* @since 1.4
*/
public synchronized StringBuffer append(StringBuffer sb) {
toStringCache = null;
super.append(sb);
return this;
}
/**
* @since 1.8
*/
@Override
synchronized StringBuffer append(AbstractStringBuilder asb) {
toStringCache = null;
super.append(asb);
return this;
}
/**
* Appends the specified {@code CharSequence} to this
* sequence.
*
* The characters of the {@code 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 {@code this}, the destination
* object, but does not synchronize on the source ({@code s}).
*
* If {@code s} is {@code null}, then the four characters
* {@code "null"} are appended.
*
* @param s the {@code CharSequence} to append.
* @return a reference to this object.
* @since 1.5
*/
@Override
public synchronized StringBuffer append(CharSequence s) {
toStringCache = null;
super.append(s);
return this;
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized StringBuffer append(CharSequence s, int start, int end)
{
toStringCache = null;
super.append(s, start, end);
return this;
}
@Override
public synchronized StringBuffer append(char[] str) {
toStringCache = null;
super.append(str);
return this;
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized StringBuffer append(char[] str, int offset, int len) {
toStringCache = null;
super.append(str, offset, len);
return this;
}
@Override
public synchronized StringBuffer append(boolean b) {
toStringCache = null;
super.append(b);
return this;
}
@Override
@HotSpotIntrinsicCandidate
public synchronized StringBuffer append(char c) {
toStringCache = null;
super.append(c);
return this;
}
@Override
@HotSpotIntrinsicCandidate
public synchronized StringBuffer append(int i) {
toStringCache = null;
super.append(i);
return this;
}
/**
* @since 1.5
*/
@Override
public synchronized StringBuffer appendCodePoint(int codePoint) {
toStringCache = null;
super.appendCodePoint(codePoint);
return this;
}
@Override
public synchronized StringBuffer append(long lng) {
toStringCache = null;
super.append(lng);
return this;
}
@Override
public synchronized StringBuffer append(float f) {
toStringCache = null;
super.append(f);
return this;
}
@Override
public synchronized StringBuffer append(double d) {
toStringCache = null;
super.append(d);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized StringBuffer delete(int start, int end) {
toStringCache = null;
super.delete(start, end);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized StringBuffer deleteCharAt(int index) {
toStringCache = null;
super.deleteCharAt(index);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized StringBuffer replace(int start, int end, String str) {
toStringCache = null;
super.replace(start, end, str);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized String substring(int start) {
return substring(start, count);
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.4
*/
@Override
public synchronized CharSequence subSequence(int start, int end) {
return super.substring(start, end);
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized String substring(int start, int end) {
return super.substring(start, end);
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
* @since 1.2
*/
@Override
public synchronized StringBuffer insert(int index, char[] str, int offset,
int len)
{
toStringCache = null;
super.insert(index, str, offset, len);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized StringBuffer insert(int offset, Object obj) {
toStringCache = null;
super.insert(offset, String.valueOf(obj));
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized StringBuffer insert(int offset, String str) {
toStringCache = null;
super.insert(offset, str);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized StringBuffer insert(int offset, char[] str) {
toStringCache = null;
super.insert(offset, str);
return this;
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public StringBuffer insert(int dstOffset, CharSequence s) {
// Note, synchronization achieved via invocations of other StringBuffer methods
// after narrowing of s to specific type
// Ditto for toStringCache clearing
super.insert(dstOffset, s);
return this;
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
* @since 1.5
*/
@Override
public synchronized StringBuffer insert(int dstOffset, CharSequence s,
int start, int end)
{
toStringCache = null;
super.insert(dstOffset, s, start, end);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public StringBuffer insert(int offset, boolean b) {
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
// after conversion of b to String by super class method
// Ditto for toStringCache clearing
super.insert(offset, b);
return this;
}
/**
* @throws IndexOutOfBoundsException {@inheritDoc}
*/
@Override
public synchronized StringBuffer insert(int offset, char c) {
toStringCache = null;
super.insert(offset, c);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public StringBuffer insert(int offset, int i) {
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
// after conversion of i to String by super class method
// Ditto for toStringCache clearing
super.insert(offset, i);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public StringBuffer insert(int offset, long l) {
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
// after conversion of l to String by super class method
// Ditto for toStringCache clearing
super.insert(offset, l);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public StringBuffer insert(int offset, float f) {
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
// after conversion of f to String by super class method
// Ditto for toStringCache clearing
super.insert(offset, f);
return this;
}
/**
* @throws StringIndexOutOfBoundsException {@inheritDoc}
*/
@Override
public StringBuffer insert(int offset, double d) {
// Note, synchronization achieved via invocation of StringBuffer insert(int, String)
// after conversion of d to String by super class method
// Ditto for toStringCache clearing
super.insert(offset, d);
return this;
}
/**
* @since 1.4
*/
@Override
public int indexOf(String str) {
// Note, synchronization achieved via invocations of other StringBuffer methods
return super.indexOf(str);
}
/**
* @since 1.4
*/
@Override
public synchronized int indexOf(String str, int fromIndex) {
return super.indexOf(str, fromIndex);
}
/**
* @since 1.4
*/
@Override
public int lastIndexOf(String str) {
// Note, synchronization achieved via invocations of other StringBuffer methods
return lastIndexOf(str, count);
}
/**
* @since 1.4
*/
@Override
public synchronized int lastIndexOf(String str, int fromIndex) {
return super.lastIndexOf(str, fromIndex);
}
/**
* @since 1.0.2
*/
@Override
public synchronized StringBuffer reverse() {
toStringCache = null;
super.reverse();
return this;
}
@Override
@HotSpotIntrinsicCandidate
@NeverInline
public synchronized String toString() {
if (toStringCache == null) {
return toStringCache =
isLatin1() ? StringLatin1.newString(value, 0, count)
: StringUTF16.newString(value, 0, count);
}
return new String(toStringCache);
}
/**
* 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();
char[] val = new char[capacity()];
if (isLatin1()) {
StringLatin1.getChars(value, 0, count, val, 0);
} else {
StringUTF16.getChars(value, 0, count, val, 0);
}
fields.put("value", val);
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();
char[] val = (char[])fields.get("value", null);
initBytes(val, 0, val.length);
count = fields.get("count", 0);
}
synchronized void getBytes(byte dst[], int dstBegin, byte coder) {
super.getBytes(dst, dstBegin, coder);
}
}