StringTokenizer in Java
- StringTokenizer
- Methods
of StringTokenizer
- Example
of StringTokenizer
The java.util.StringTokenizer class allows you to break a string
into tokens. It is simple way to break string.
It doesn't provide the facility
to differentiate numbers, quoted strings, identifiers etc. like StreamTokenizer
class. We will discuss about the StreamTokenizer class in I/O chapter.
Constructors of
StringTokenizer class
There are 3 constructors
defined in the StringTokenizer class.
|
Constructor
|
Description
|
|
StringTokenizer(String
str)
|
creates
StringTokenizer with specified string.
|
|
StringTokenizer(String
str, String delim)
|
creates
StringTokenizer with specified string and delimeter.
|
|
StringTokenizer(String
str, String delim, boolean returnValue)
|
creates
StringTokenizer with specified string, delimeter and returnValue. If return
value is true, delimiter characters are considered to be tokens. If it is
false, delimiter characters serve to separate tokens.
|
Methods of StringTokenizer
class
The 6 useful methods of
StringTokenizer class are as follows:
|
Public method
|
Description
|
|
boolean
hasMoreTokens()
|
checks
if there is more tokens available.
|
|
String
nextToken()
|
returns
the next token from the StringTokenizer object.
|
|
String
nextToken(String delim)
|
returns
the next token based on the delimeter.
|
|
boolean
hasMoreElements()
|
same
as hasMoreTokens() method.
|
|
Object
nextElement()
|
same
as nextToken() but its return type is Object.
|
|
int countTokens()
|
returns
the total number of tokens.
|
Simple
example of StringTokenizer class
Let's see the simple example of
StringTokenizer class that tokenizes a string "my name is khan" on
the basis of whitespace.
1.
import java.util.StringTokenizer;
2.
public class Simple{
3.
public static void main(String args[]){
4.
StringTokenizer st = new StringTokenizer("my name is khan"," ");
5.
while (st.hasMoreTokens()) {
6.
System.out.println(st.nextToken());
7.
}
8.
}
9.
}
Output:my
name
is
khan
Example of
nextToken(String delim) method of StringTokenizer class
1. import java.util.*;
2.
3. public class Test {
4. public static void main(String[] args) {
5. StringTokenizer st = new StringTokenizer("my,name,is,khan");
6.
7. // printing next token
8. System.out.println("Next token is : " + st.nextToken(","));
9. }
10. }
Output:Next token is : my
StringTokenizer
class is deprecated now. It is recommended to use split() method of String
class or regex (Regular Expression).
Java String charAt
The java string charAt() method returns a char value at the
given index number. The index number starts from 0.
Signature
The signature of string
charAt() method is given below:
1. public char charAt(int index)
Parameter
index : index number, starts with 0
Returns
char value
Specified
by
CharSequence interface
Throws
IndexOutOfBoundsException : if index is negative value or greater
than this string length.
Java String charAt() method example
1. public class CharAtExample{
2. public static void main(String args[]){
3. String name="javatpoint";
4. char ch=name.charAt(4);//returns the char value at the 4th index
5. System.out.println(ch);
6. }}
t
Java String compareTo
The java string compareTo() method compares the given string with
current string lexicographically. It returns positive number, negative number
or 0.
If first string is greater than
second string, it returns positive number (difference of character value). If
first string is less than second string, it returns negative number and if
first string is equal to second string, it returns 0.
1. s1 > s2 => positive number
2. s1 < s2 => negative number
3. s1 == s2 => 0
Signature
1. public int compareTo(String anotherString)
Parameters
anotherString:
represents string that is to be compared with current string
Returns
an integer value
Java String compareTo() method example
1. public class LastIndexOfExample{
2. public static void main(String args[]){
3. String s1="hello";
4. String s2="hello";
5. String s3="meklo";
6. String s4="hemlo";
7. System.out.println(s1.compareTo(s2));
8. System.out.println(s1.compareTo(s3));
9. System.out.println(s1.compareTo(s4));
10. }}
Output:
0
-5
-1
Java String concat
The java string concat() method combines
specified string at the end of this string. It returns combined
string. It is like appending another string.
Signature
The signature of string
concat() method is given below:
1. public String concat(String anotherString)
Parameter
anotherString : another string i.e. to be combined at the
end of this string.
Returns
combined string
Java String concat() method example
1.
public class ConcatExample{
2.
public static void main(String args[]){
3.
String s1="java string";
4.
s1.concat("is immutable");
5.
System.out.println(s1);
6.
s1=s1.concat(" is immutable so assign it explicitly");
7.
System.out.println(s1);
8.
}}
java string
java string is immutable so assign it explicitly
Java String contains
The java string contains() method searches the sequence of
characters in this string. It returns true if sequence of char values are found
in this string otherwise returns false.
Signature
The signature of string
contains() method is given below:
1.
public boolean contains(CharSequence sequence)
Parameter
sequence : specifies the sequence of characters to
be searched.
Returns
true if sequence of char value exists, otherwise false.
Throws
NullPointerException : if sequence is null.
Java String contains() method example
1.
class ContainsExample{
2.
public static void main(String args[]){
3.
String name="what do you know about me";
4.
System.out.println(name.contains("do you know"));
5.
System.out.println(name.contains("about"));
6.
System.out.println(name.contains("hello"));
7.
}}
true
true
false
Java String endsWith
The java
string endsWith() method
checks if this string ends with given suffix. It returns true if this string
ends with given suffix else returns false.
Signature
The syntax or signature of
endsWith() method is given below.
1.
public boolean endsWith(String suffix)
Parameter
suffix : Sequence of character
Returns
true or false
Java String endsWith() method example
1.
public class EndsWithExample{
2.
public static void main(String args[]){
3.
String s1="java by javatpoint";
4.
System.out.println(s1.endsWith("t"));
5.
System.out.println(s1.startsWith("point"));
6.
}}
Output:
true
true
Java String equals
The java string equals() method compares the two given strings
based on the content of the string. If any character is not matched, it returns
false. If all characters are matched, it returns true.
The String equals() method
overrides the equals() method of Object class.
Signature
1. public boolean equals(Object anotherObject)
Parameter
anotherObject : another object i.e. compared with this
string.
Returns
true if characters of both strings are equal
otherwise false.
Overrides
equals() method of java Object
class.
Java String equals() method example
1. public class EqualsExample{
2. public static void main(String args[]){
3. String s1="javatpoint";
4. String s2="javatpoint";
5. String s3="JAVATPOINT";
6. String s4="python";
7. System.out.println(s1.equals(s2));//true because content and case is same
8. System.out.println(s1.equals(s3));//false because case is not same
9. System.out.println(s1.equals(s4));//false because content is not same
10. }}
true
false
false
Java String format
The java string format() method returns the formatted string by
given locale, format and arguments.
If you don't specify the locale
in String.format() method, it uses default locale by callingLocale.getDefault() method.
The format() method of java
language is like sprintf() function in c language and printf() method of java language.
Signature
There are two type of string
format() method:
1. public static String format(String format, Object... args)
2. and,
3. public static String format(Locale locale, String format, Object... args)
Parameters
locale : specifies the locale to be applied on the
format() method.
format : format of the string.
args : arguments for the format string. It may
be zero or more.
Returns
formatted string
Throws
NullPointerException : if format is null.
IllegalFormatException : if format is illegal or incompatible.
Java String format() method example
1. public class FormatExample{
2. public static void main(String args[]){
3. String name="sonoo";
4. String sf1=String.format("name is %s",name);
5. String sf2=String.format("value is %f",32.33434);
6. String sf3=String.format("value is %32.12f",32.33434);//returns 12 char fractional part filling with 0
7.
8. System.out.println(sf1);
9. System.out.println(sf2);
10. System.out.println(sf3);
11. }}
name is sonoo
value is 32.334340
value is 32.334340000000
Java String getBytes()
The java string getBytes() method returns the byte array of the
string. In other words, it returns sequence of bytes.
Signature
There are 3 variant of
getBytes() method. The signature or syntax of string getBytes() method is given
below:
1. public byte[] getBytes()
2. public byte[] getBytes(Charset charset)
3. public byte[] getBytes(String charsetName)throws UnsupportedEncodingException
Returns
sequence of bytes.
Java String getBytes() method example
1. public class StringGetBytesExample{
2. public static void main(String args[]){
3. String s1="ABCDEFG";
4. byte[] barr=s1.getBytes();
5. for(int i=0;i<barr.length;i++){
6. System.out.println(barr[i]);
7. }
8. }}
Output:
65
66
67
68
69
70
71
Java String indexOf
The java string indexOf() method returns index of given
character value or substring. If it is not found, it returns -1. The index
counter starts from zero.
Signature
There are 4 types of indexOf
method in java. The signature of indexOf methods are given below:
|
No.
|
Method
|
Description
|
|
1
|
int
indexOf(int ch)
|
returns
index position for the given char value
|
|
2
|
int
indexOf(int ch, int fromIndex)
|
returns
index position for the given char value and from index
|
|
3
|
int
indexOf(String substring)
|
returns
index position for the given substring
|
|
4
|
int
indexOf(String substring, int fromIndex)
|
returns
index position for the given substring and from index
|
Parameters
ch: char
value i.e. a single character e.g. 'a'
fromIndex: index
position from where index of the char value or substring is retured
substring:
substring to be searched in this string
Returns
index of the string
Java String indexOf() method example
1. public class IndexOfExample{
2. public static void main(String args[]){
3. String s1="this is index of example";
4. //passing substring
5. int index1=s1.indexOf("is");//returns the index of is substring
6. int index2=s1.indexOf("index");//returns the index of index substring
7. System.out.println(index1+" "+index2);//2 8
8.
9. //passing substring with from index
10. int index3=s1.indexOf("is",4);//returns the index of is substring after 4th index
11. System.out.println(index3);//5 i.e. the index of another is
12.
13. //passing char value
14. int index4=s1.indexOf('s');//returns the index of s char value
15. System.out.println(index4);//3
16. }}
2 8
5
3
Java String intern
The java string intern() method returns the interned string. It
returns the canonical representation of string.
It can be used to return string
from pool memory, if it is created by new keyword.
Signature
The signature of intern method
is given below:
1. public String intern()
Returns
interned string
Java String intern() method example
1. public class InternExample{
2. public static void main(String args[]){
3. String s1=new String("hello");
4. String s2="hello";
5. String s3=s1.intern();//returns string from pool, now it will be same as s2
6. System.out.println(s1==s2);//false because reference is different
7. System.out.println(s2==s3);//true because reference is same
8. }}
false
true
Java String isEmpty
The java string isEmpty() method checks if this string is empty.
It returns true, if length
of string is 0 otherwise false.
The isEmpty() method of String
class is included in java string since JDK 1.6.
Signature
The signature or syntax of
string isEmpty() method is given below:
1. public boolean isEmpty()
Returns
true if length is 0 otherwise
false.
Since
1.6
Java String isEmpty() method example
1. public class IsEmptyExample{
2. public static void main(String args[]){
3. String s1="";
4. String s2="javatpoint";
5.
6. System.out.println(s1.isEmpty());
7. System.out.println(s2.isEmpty());
8. }}
true
false
Java String join
The java string join() method returns a string joined with
given delimiter. In string join method, delimiter is copied for each elements.
In case of null element,
"null" is added. The join() method is included in java string since
JDK 1.8.
There are two types of join()
methods in java string.
Signature
The signature or syntax of string
join method is given below:
1. public static String join(CharSequence delimiter, CharSequence... elements)
2. and
3. public static String join(CharSequence delimiter, Iterable<? extends CharSequence> elements)
Parameters
delimiter : char value to be added with each element
elements : char value to be attached with delimiter
Returns
joined string with delimiter
Throws
NullPointerException if element or delimiter is null.
Since
1.8
Java String join() method example
1. public class StringJoinExample{
2. public static void main(String args[]){
3. String joinString1=String.join("-","welcome","to","javatpoint");
4. System.out.println(joinString1);
5. }}
welcome-to-javatpoint
Java String lastIndexOf
The java string lastIndexOf() method returns last index of the given
character value or substring. If it is not found, it returns -1. The index
counter starts from zero.
Signature
There are 4 types of
lastIndexOf method in java. The signature of lastIndexOf methods are given
below:
|
No.
|
Method
|
Description
|
|
1
|
int
lastIndexOf(int ch)
|
returns
last index position for the given char value
|
|
2
|
int
lastIndexOf(int ch, int fromIndex)
|
returns
last index position for the given char value and from index
|
|
3
|
int
lastIndexOf(String substring)
|
returns
last index position for the given substring
|
|
4
|
int
lastIndexOf(String substring, int fromIndex)
|
returns
last index position for the given substring and from index
|
Parameters
ch: char
value i.e. a single character e.g. 'a'
fromIndex: index
position from where index of the char value or substring is retured
substring:
substring to be searched in this string
Returns
last index of the string
Java String lastIndexOf() method example
1. public class LastIndexOfExample{
2. public static void main(String args[]){
3. String s1="this is index of example";//there are 2 's' characters in this sentence
4. int index1=s1.lastIndexOf('s');//returns last index of 's' char value
5. System.out.println(index1);//6
6. }}
Output:
6
Java String length
The java string length() method length of the string. It
returns count of total number of characters. The length of java string is same
as the unicode code units of the string.
Signature
The signature of the string
length() method is given below:
1. public int length()
Specified by
CharSequence interface
Returns
length of characters
Java String length() method example
1. public class LengthExample{
2. public static void main(String args[]){
3. String s1="javatpoint";
4. String s2="python";
5. System.out.println("string length is: "+s1.length());//10 is the length of javatpoint string
6. System.out.println("string length is: "+s2.length());//6 is the length of python string
7. }}
string length is: 10
string length is: 6
Java String replace
The java string replace() method returns a string replacing all
the old char or CharSequence to new char or CharSequence.
Since JDK 1.5, a new replace()
method is introduced, allowing you to replace a sequence of char values.
Signature
There are two type of replace
methods in java string.
1.
public String replace(char oldChar, char newChar)
2.
and
3.
public String replace(CharSequence target, CharSequence replacement)
The second replace method is
added since JDK 1.5.
Parameters
oldChar : old character
newChar : new character
target : target sequence of characters
replacement : replacement sequence of characters
Returns
replaced string
Java
String replace(char old, char new) method example
1. public class ReplaceExample1{
2. public static void main(String args[]){
3. String s1="javatpoint is a very good website";
4. String replaceString=s1.replace('a','e');//replaces all occurrences of 'a' to 'e'
5. System.out.println(replaceString);
6. }}
jevetpoint is e very good website
Java
String replace(CharSequence target, CharSequence replacement) method example
1. public class ReplaceExample2{
2. public static void main(String args[]){
3. String s1="my name is khan my name is java";
4. String replaceString=s1.replace("is","was");//replaces all occurrences of "is" to "was"
5. System.out.println(replaceString);
6. }}
my name was khan my name was java
Java String replaceAll
The java string replaceAll() method returns a string replacing all
the sequence of characters matching regex and replacement string.
Signature
1.
public String replaceAll(String regex, String replacement)
Parameters
regex : regular expression
replacement : replacement sequence of characters
Returns
replaced string
Java
String replaceAll() example: replace character
Let's see an example to replace
all the occurrences of a single character.
1. public class ReplaceAllExample1{
2. public static void main(String args[]){
3. String s1="javatpoint is a very good website";
4. String replaceString=s1.replaceAll("a","e");//replaces all occurrences of "a" to "e"
5. System.out.println(replaceString);
6. }}
jevetpoint is e very good website
Java
String replaceAll() example: replace word
Let's see an example to replace
all the occurrences of single word or set of words.
1. public class ReplaceAllExample2{
2. public static void main(String args[]){
3. String s1="My name is Khan. My name is Bob. My name is Sonoo.";
4. String replaceString=s1.replaceAll("is","was");//replaces all occurrences of "is" to "was"
5. System.out.println(replaceString);
6. }}
My name was Khan. My name was Bob. My name was Sonoo.
Java
String replaceAll() example: remove white spaces
Let's see an example to remove
all the occurrences of white spaces.
1.
public class ReplaceAllExample3{
2.
public static void main(String args[]){
3.
String s1="My name is Khan. My name is Bob. My name is Sonoo.";
4.
String replaceString=s1.replaceAll("\\s","");
5.
System.out.println(replaceString);
6.
}}
MynamewasKhan.MynamewasBob.MynamewasSonoo.
ava String split
The java string split() method splits this string against
given regular expression and returns a char array.
Signature
There are two signature for
split() method in java string.
1.
public String split(String regex)
2.
and,
3.
public String split(String regex, int limit)
Parameter
regex : regular expression to be applied on
string.
limit : limit for the number of strings in array.
If it is zero, it will returns all the strings matching regex.
Returns
array of strings
Throws
PatternSyntaxException if pattern for regular expression is
invalid
Since
1.4
Java String split() method example
The given example returns total
number of words in a string excluding space only. It also includes special
characters.
1.
public class SplitExample{
2.
public static void main(String args[]){
3.
String s1="java string split method by javatpoint";
4.
String[] words=s1.split("\\s");//splits the string based on string
5.
//using java foreach loop to print elements of string array
6.
for(String w:words){
7.
System.out.println(w);
8.
}
9.
}}
java
string
split
method
by
javatpoint
Java String split() method with regex and length example
1.
public class SplitExample2{
2.
public static void main(String args[]){
3.
String s1="welcome to split world";
4.
System.out.println("returning words:");
5.
for(String w:s1.split("\\s",0)){
6.
System.out.println(w);
7.
}
8.
System.out.println("returning words:");
9.
for(String w:s1.split("\\s",1)){
10. System.out.println(w);
11. }
12. System.out.println("returning words:");
13. for(String w:s1.split("\\s",2)){
14. System.out.println(w);
15. }
16.
17. }}
returning words:
welcome
to
split
world
returning words:
welcome to split world
returning words:
welcome
to split world
Java String startsWith
The java
string startsWith() method
checks if this string starts with given prefix. It returns true if this string
starts with given prefix else returns false.
Signature
The syntax or signature of
startWith() method is given below.
1.
public boolean startsWith(String prefix)
2.
public boolean startsWith(String prefix, int offset)
Parameter
prefix : Sequence of character
Returns
true or false
Java String startsWith() method example
1.
public class StartsWithExample{
2.
public static void main(String args[]){
3.
String s1="java string split method by javatpoint";
4.
System.out.println(s1.startsWith("ja"));
5.
System.out.println(s1.startsWith("java string"));
6.
}}
Output:
true
true
Java String substring
The java string substring() method returns a part of the string.
We pass begin index and end
index number position in the java substring method where start index is
inclusive and end index is exclusive. In other words, start index starts from 0
whereas end index starts from 1.
There are two types of
substring methods in java string.
Signature
1.
public String substring(int startIndex)
2.
and
3.
public String substring(int startIndex, int endIndex)
If you don't specify endIndex,
java substring() method will return all the characters from startIndex.
Parameters
startIndex : starting index is inclusive
endIndex : ending index is exclusive
Returns
specified string
Throws
StringIndexOutOfBoundsException if start index is negative value or end
index is lower than starting index.
Java String substring() method example
1.
public class SubstringExample{
2.
public static void main(String args[]){
3.
String s1="javatpoint";
4.
System.out.println(s1.substring(2,4));//returns va
5.
System.out.println(s1.substring(2));//returns vatpoint
6.
}}
va
vatpoint
Java String toCharArray
The java
string toCharArray() method
converts this string into character array. It returns a newly created character
array, its length is similar to this string and its contents are initialized
with the characters of this string.
Signature
The signature or syntax of
string toCharArray() method is given below:
1.
public char[] toCharArray()
Returns
character array
Java String toCharArray() method example
1.
public class StringToCharArrayExample{
2.
public static void main(String args[]){
3.
String s1="hello";
4.
char[] ch=s1.toCharArray();
5.
for(int i=0;i<ch.length;i++){
6.
System.out.print(ch[i]);
7.
}
8.
}}
Output:
hello
Java String toLowerCase()
The java string toLowerCase() method returns the string in lowercase
letter. In other words, it converts all characters of the string into lower
case letter.
The toLowerCase() method works
same as toLowerCase(Locale.getDefault()) method. It internally uses the default
locale.
Signature
There are two variant of
toLowerCase() method. The signature or syntax of string toLowerCase() method is
given below:
1. public String toLowerCase()
2. public String toLowerCase(Locale locale)
The second method variant of
toLowerCase(), converts all the characters into lowercase using the rules of
given Locale.
Returns
string in lowercase letter.
Java String toLowerCase() method example
1. public class StringLowerExample{
2. public static void main(String args[]){
3. String s1="JAVATPOINT HELLO stRIng";
4. String s1lower=s1.toLowerCase();
5. System.out.println(s1lower);
6. }}
Output:
javatpoint hello string
Java String toUpperCase
The java string toUpperCase() method returns the string in uppercase
letter. In other words, it converts all characters of the string into upper
case letter.
The toUpperCase() method works
same as toUpperCase(Locale.getDefault()) method. It internally uses the default
locale.
Signature
There are two variant of
toUpperCase() method. The signature or syntax of string toUpperCase() method is
given below:
1. public String toUpperCase()
2. public String toUpperCase(Locale locale)
The second method variant of
toUpperCase(), converts all the characters into uppercase using the rules of
given Locale.
Returns
string in uppercase letter.
Java String toUpperCase() method example
1. public class StringUpperExample{
2. public static void main(String args[]){
3. String s1="hello string";
4. String s1upper=s1.toUpperCase();
5. System.out.println(s1upper);
6. }}
Output:
HELLO STRING
Java String trim
The java string trim() method eliminates leading and trailing
spaces. The unicode value of space character is '\u0020'. The trim() method in
java string checks this unicode value before and after the string, if it exists
then removes the spaces and returns the omitted string.
The
string trim() method doesn't omits middle spaces.
Signature
The signature or syntax of
string trim method is given below:
1. public String trim()
Returns
string with omitted leading and
trailing spaces
Java String trim() method example
1. public class StringTrimExample{
2. public static void main(String args[]){
3. String s1=" hello string ";
4. System.out.println(s1+"javatpoint");//without trim()
5. System.out.println(s1.trim()+"javatpoint");//with trim()
6. }}
hello string javatpoint
hello stringjavatpoint
Java String valueOf
The java
string valueOf() method
converts different types of values into string. By the help of string valueOf()
method, you can convert int to string, long to string, boolean to string,
character to string, float to string, double to string, object to string and
char array to string.
Signature
The signature or syntax of
string valueOf() method is given below:
1. public static String valueOf(boolean b)
2. public static String valueOf(char c)
3. public static String valueOf(char[] c)
4. public static String valueOf(int i)
5. public static String valueOf(long l)
6. public static String valueOf(float f)
7. public static String valueOf(double d)
8. public static String valueOf(Object o)
Returns
string representation of given
value
Java String valueOf() method example
1. public class StringValueOfExample{
2. public static void main(String args[]){
3. int value=30;
4. String s1=String.valueOf(value);
5. System.out.println(s1+10);//concatenating string with 10
6. }}
Output:
3010
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