StringBuilder objects are String objects that can be modified. Hence to create a mutable (modifiable) string object, we use the Java StringBuilder class.
StringBuilder is not thread-safe or, in other words, not synchronized. One should prefer using StringBuffer if synchronization is mandatory.
The class is designed for use as a drop-in replacement for StringBuffer in places where the String Buffer used by a single thread.
Class Hierarchy – java.lang.Object -> java.lang-> Class StringBuilder
Constructors of StringBuilder Class –
StringBuilder ( ) – This constructor constructs a string builder with no characters in it and an initial capacity of 16 characters.
StringBuilder ( int capacity ) – This constructor constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
StringBuilder(CharSequence seq) – This constructor constructs a string builder that contains the same characters as the specified CharSequence.
StringBuilder ( String str ) – This constructor constructs a string builder initialized to the specified string’s contents. Also, the initial capacity of the string builder is 16 plus the length of the string argument.
Some methods of StringBuilder class –
append () – It concatenates the given argument(string representation) to the end of the invoking StringBuilder object.
insert() – It inserts the given argument(string representation) into the invoking StringBuilder object at the given position.
replace() – It replaces the string from a specified start index to the end index.
reverse() – It reverses the characters within a StringBuilder object.
delete() – It deletes the string from the specified beginIndex to the endIndex.
capacity() – It returns the current capacity of the StringBuilder object.
String Buffer –
StringBufferis a peer class of String that creates mutable (modifiable) string, i.e., it represents growable and writable character sequences.
One may insert characters and substrings in the middle or append them to the end in StringBuffer. It will automatically grow to make room for such additions and often pre-allocate more characters than we need to allow room for growth.
StringBuffer is thread-safe; most of its methods are synchronized. So multiple threads cannot access or use the StringBuffer object at the same time.
Constructors of StringBuffer Class –
StringBuffer( ) – This constructor reserves room for 16 characters without reallocation.
StringBuffer( int size) – This constructor accepts an integer argument that explicitly sets the buffer’s size.
StringBuffer(String str) – This constructor accepts a String argument and sets the StringBuffer object’s initial contents. Also, it reserves room for 16 more characters without reallocation.
Some methods of StringBuffer class –
length() – It returns the StringBuffer object’s length.
capacity() – It returns the capacity of the StringBuffer object.
append( ) – It adds text at the end of the existing text.
insert( ) – It inserts text at the specified index position.
reverse( ) – It reverses the characters within a StringBuffer object. It will return the reversed object on which this method was called.
ensureCapacity( ) – It increases the capacity of a StringBuffer object and ensures that the capacity is equal to the given minimum.
String Tokenizer –
An application can break a string into tokens with the help of StringTokenizer class. It is a simple way to break a string.
It does not have the facility to differentiate between numbers, quoted strings, identifiers, etc.
A current position is maintained internally by the StringTokenizer object within the string to be tokenized.
Constructors of StringTokenizer Class –
StringTokenizer(String str) – It accepts a string that needs to be tokenized. The default delimiters used are new line, space, tab, carriage return, and form feed.
StringTokenizer(String str, String delim) – It accepts a string and a set of delimiters used to tokenize the given string.
StringTokenizer(String str, String delim, boolean flag) -It accepts a string, set of delimiters, and a flag. If the flag is true, delimiter characters are considered to be tokens. If the flag is false, delimiter characters serve to separate tokens.
Some methods of StringTokenizer Class –
hasMoreTokens() – It checks if there are more tokens available.
nextToken() – It returns the next token from the StringTokenizer object.
nextToken(String delim) – It returns the next token based on the delimiter.
hasMoreElements() – It is same as hasMoreTokens() method.
nextElement() – It is same as nextToken() but its return type is Object.
countTokens() – It returns the total number of tokens.