The string tokenizer class allows an application to break a string
into tokens by performing code point comparison.
The
StringTokenizer
methods do not distinguish
among identifiers, numbers, and quoted strings, nor do they recognize
and skip comments.
The set of delimiters (the codepoints that separate tokens) may be
specified either at creation time or on a per-token basis.
An instance of
StringTokenizer
behaves in one of three ways,
depending on whether it was created with the
returnDelims
and
coalesceDelims
flags having the value
true
or
false
:
- If returnDelims is
false
, delimiter code points serve to
separate tokens. A token is a maximal sequence of consecutive
code points that are not delimiters.
- If returnDelims is
true
, delimiter code points are
themselves considered to be tokens. In this case, if coalesceDelims is
true
, such tokens will be the maximal sequence of consecutive
code points that are delimiters. If coalesceDelims is false,
a token will be received for each delimiter code point.
A token is thus either one
delimiter code point, a maximal sequence of consecutive code points that
are delimiters, or a maximal sequence of consecutive code
points that are not delimiters.
A
StringTokenizer object internally maintains a current
position within the string to be tokenized. Some operations advance this
current position past the code point processed.
A token is returned by taking a substring of the string that was used to
create the
StringTokenizer object.
Example of the use of the default delimiter tokenizer.
StringTokenizer st = new StringTokenizer("this is a test");
while (st.hasMoreTokens()) {
println(st.nextToken());
}
prints the following output:
this
is
a
test
Example of the use of the tokenizer with user specified delimiter.
StringTokenizer st = new StringTokenizer(
"this is a test with supplementary characters \ud800\ud800\udc00\udc00",
" \ud800\udc00");
while (st.hasMoreTokens()) {
println(st.nextToken());
}
prints the following output:
this
is
a
test
with
supplementary
characters
\ud800
\udc00
StringTokenizer
public StringTokenizer(String str)
Constructs a string tokenizer for the specified string.
The tokenizer uses the default delimiter set, which is
" \t\n\r\f":
the space character, the tab character, the newline character, the
carriage-return character, and the form-feed character.
Delimiter characters themselves will not be treated as tokens.
str
- a string to be parsed
StringTokenizer
public StringTokenizer(String str,
String delim)
Constructs a string tokenizer for the specified string. The
characters in the delim argument are the delimiters for separating
tokens.
Delimiter characters themselves will not be treated as tokens.
str
- a string to be parsed.delim
- the delimiters.
StringTokenizer
public StringTokenizer(String str,
String delim,
boolean returndelims)
Constructs a string tokenizer for the specified string. All
characters in the delim argument are the delimiters for separating
tokens.
If the returnDelims flag is false, the delimiter characters are
skipped and only serve as separators between tokens.
If the returnDelims flag is true, then the delimiter characters
are also returned as tokens, one per delimiter.
str
- a string to be parsed.delim
- the delimiters.returndelims
- flag indicating whether to return the delimiters
as tokens.
StringTokenizer
public StringTokenizer(String str,
String delim,
boolean returndelims,
boolean coalescedelims)
This API is ICU internal only.
Constructs a string tokenizer for the specified string. All
characters in the delim argument are the delimiters for separating
tokens.
If the returnDelims flag is false, the delimiter characters are
skipped and only serve as separators between tokens.
If the returnDelims flag is true, then the delimiter characters
are also returned as tokens. If coalescedelims is true, one token
is returned for each run of delimiter characters, otherwise one
token is returned per delimiter. Since surrogate pairs can be
delimiters, the returned token might be two chars in length.
str
- a string to be parsed.delim
- the delimiters.returndelims
- flag indicating whether to return the delimiters
as tokens.coalescedelims
- flag indicating whether to return a run of
delimiters as a single token or as one token per delimiter.
This only takes effect if returndelims is true.
StringTokenizer
public StringTokenizer(String str,
UnicodeSet delim)
Constructs a string tokenizer for the specified string. The
characters in the delim argument are the delimiters for separating
tokens.
Delimiter characters themselves will not be treated as tokens.
str
- a string to be parsed.delim
- the delimiters.
StringTokenizer
public StringTokenizer(String str,
UnicodeSet delim,
boolean returndelims)
Constructs a string tokenizer for the specified string. All
characters in the delim argument are the delimiters for separating
tokens.
If the returnDelims flag is false, the delimiter characters are
skipped and only serve as separators between tokens.
If the returnDelims flag is true, then the delimiter characters
are also returned as tokens, one per delimiter.
str
- a string to be parsed.delim
- the delimiters.returndelims
- flag indicating whether to return the delimiters
as tokens.
StringTokenizer
public StringTokenizer(String str,
UnicodeSet delim,
boolean returndelims,
boolean coalescedelims)
This API is ICU internal only.
Constructs a string tokenizer for the specified string. All
characters in the delim argument are the delimiters for separating
tokens.
If the returnDelims flag is false, the delimiter characters are
skipped and only serve as separators between tokens.
If the returnDelims flag is true, then the delimiter characters
are also returned as tokens. If coalescedelims is true, one token
is returned for each run of delimiter characters, otherwise one
token is returned per delimiter. Since surrogate pairs can be
delimiters, the returned token might be two chars in length.
str
- a string to be parsed.delim
- the delimiters.returndelims
- flag indicating whether to return the delimiters
as tokens.coalescedelims
- flag indicating whether to return a run of
delimiters as a single token or as one token per delimiter.
This only takes effect if returndelims is true.
countTokens
public int countTokens()
Calculates the number of times that this tokenizer's
nextToken
method can be called before it generates an
exception. The current position is not advanced.
- the number of tokens remaining in the string using the
current delimiter set.
hasMoreElements
public boolean hasMoreElements()
Returns the same value as the hasMoreTokens
method.
It exists so that this class can implement the
Enumeration
interface.
true
if there are more tokens;
false
otherwise.
hasMoreTokens
public boolean hasMoreTokens()
Tests if there are more tokens available from this tokenizer's
string.
If this method returns true, then a subsequent call to
nextToken with no argument will successfully return a token.
true
if and only if there is at least one token
in the string after the current position; false
otherwise.
nextElement
public Object nextElement()
Returns the same value as the nextToken
method, except
that its declared return value is Object
rather than
String
. It exists so that this class can implement the
Enumeration
interface.
- the next token in the string.
nextToken
public String nextToken()
Returns the next token from this string tokenizer.
- the next token from this string tokenizer.
nextToken
public String nextToken(String delim)
Returns the next token in this string tokenizer's string. First,
the set of characters considered to be delimiters by this
StringTokenizer object is changed to be the characters in
the string delim. Then the next token in the string
after the current position is returned. The current position is
advanced beyond the recognized token. The new delimiter set
remains the default after this call.
delim
- the new delimiters.
- the next token, after switching to the new delimiter set.
nextToken
public String nextToken(UnicodeSet delim)
Returns the next token in this string tokenizer's string. First,
the set of characters considered to be delimiters by this
StringTokenizer object is changed to be the characters in
the string delim. Then the next token in the string
after the current position is returned. The current position is
advanced beyond the recognized token. The new delimiter set
remains the default after this call.
delim
- the new delimiters.
- the next token, after switching to the new delimiter set.