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Object | +----java.lang.StringBuffer
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.
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".
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.
java.lang.StringBuffer()
java.lang.StringBuffer(int)
length argument.
java.lang.StringBuffer(String)
append(Object)
Object
argument to this string buffer.
append(String)
append(char[])
char array
argument to this string buffer.
append(char[], int, int)
char array argument to this string buffer.
append(boolean)
boolean
argument to the string buffer.
append(char)
char
argument to this string buffer.
append(int)
int
argument to this string buffer.
append(long)
long
argument to this string buffer.
append(float)
float
argument to this string buffer.
append(double)
double
argument to this string buffer.
capacity()
charAt(int)
ensureCapacity(int)
getChars(int, int, char[], int)
dst.
insert(int, Object)
Object
argument into this string buffer.
insert(int, String)
insert(int, char[])
char array
argument into this string buffer.
insert(int, boolean)
boolean
argument into this string buffer.
insert(int, char)
char
argument into this string buffer.
insert(int, int)
int
argument into this string buffer.
insert(int, long)
long
argument into this string buffer.
insert(int, float)
float
argument into this string buffer.
insert(int, double)
double
argument into this string buffer.
length()
reverse()
setCharAt(int, char)
ch.
setLength(int)
toString()
StringBuffer
public StringBuffer()
StringBuffer
public StringBuffer(int length)
length argument.
length
argument is less than 0.
StringBuffer
public StringBuffer(String str)
16 plus the length
of the string argument.
append
public synchronized java.lang.StringBuffer append(Object obj)
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.
Object.
append
public synchronized java.lang.StringBuffer append(String str)
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.
append
public synchronized java.lang.StringBuffer append(char str)
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.
append
public synchronized java.lang.StringBuffer append(char str,
int offset,
int len)
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.
append
public java.lang.StringBuffer append(boolean b)
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.
boolean.
append
public synchronized java.lang.StringBuffer append(char c)
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.
char.
append
public java.lang.StringBuffer append(int i)
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.
int.
append
public java.lang.StringBuffer append(long l)
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.
long.
append
public java.lang.StringBuffer append(float f)
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.
float.
append
public java.lang.StringBuffer append(double d)
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.
double.
capacity
public int capacity()
charAt
public synchronized char charAt(int index)
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.
ensureCapacity
public synchronized void ensureCapacity(int minimumCapacity)
minimumCapacity argument.
2.
minimumCapacity argument is nonpositive, this
method takes no action and simply returns.
getChars
public synchronized void getChars(int srcBegin,
int srcEnd,
char dst,
int dstBegin)
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.
insert
public synchronized java.lang.StringBuffer insert(int offset,
Object obj)
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.
Object.
insert
public synchronized java.lang.StringBuffer insert(int offset,
String str)
The characters of the String 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.
The offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.
insert
public synchronized java.lang.StringBuffer insert(int offset,
char str)
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.
insert
public java.lang.StringBuffer insert(int offset,
boolean b)
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.
boolean.
insert
public synchronized java.lang.StringBuffer insert(int offset,
char c)
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 offset argument must be greater than or equal to
0, and less than or equal to the length of this
string buffer.
char.
insert
public java.lang.StringBuffer insert(int offset,
int i)
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.
int.
insert
public java.lang.StringBuffer insert(int offset,
long l)
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 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.
long.
insert
public java.lang.StringBuffer insert(int offset,
float f)
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.
float.
insert
public java.lang.StringBuffer insert(int offset,
double d)
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.
double.
length
public int length()
reverse
public synchronized java.lang.StringBuffer reverse()
setCharAt
public synchronized void setCharAt(int index,
char ch)
ch.
The offset argument must be greater than or equal to
0, and less than the length of this string buffer.
setLength
public synchronized void setLength(int newLength)
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.
newLength argument is invalid.
toString
public java.lang.String toString()
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.
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