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Java StringBuilder Class

A mutable string of characters is represented by the Java class StringBuilder. The StringBuilder class offers a substitute for the String Class in Java because it creates a mutable sequence of characters instead of an immutable one like the String Class does. The functions of the StringBuilder and StringBuffer classes are very similar because both create mutable sequences of characters as an alternative to the String Class.

However, synchronization is where the StringBuilder class and StringBuffer class diverge. Contrary to the StringBuffer class, the StringBuilder class does not guarantee synchronization. As a result, this class is intended to be used in places where a single thread previously used the StringBuffer as a drop-in replacement (as is generally the case). It is advised to use this class instead of StringBuffer whenever possible because it will typically be faster in most implementations.

StringBuilder instances should not be used by multiple threads. The use of StringBuffer is advised if such synchronization is necessary. In comparison to String buffer, String Builder performs well but is not thread-safe.

Class hierarchy

java.lang.Object
 ↳ java.lang
    ↳ Class StringBuilder

Important Constructors of StringBuilder Class

StringBuilder() : StringBuilder() generates a blank StringBuilder with a 16-character initial capacity.

StringBuilder s = new StringBuilder();

StringBuilder(String str) : Creates a String Builder with the specified string by calling String Builder(String String_variable_name).

String Builder s = new StringBuilder(10);

StringBuilder(int capacity) : StringBuilder(int capacity) creates an empty String Builder with the capacity specified as its length.

StringBuilder s = new StringBuilder("DockerTpoint");

Important methods of StringBuilder class

Java String append() Methods

The append() method of the StringBuilder class concatenates the given argument with this string.

 // Java example of String length() Methods

public class Main {	
    public static void main(String args[]){  		 
      StringBuilder sb = new StringBuilder("Exam");
      sb.append("Deva"); //  original string is changed
      System.out.println(sb);
  } 
}

Output:

DockerTpoint

Java String insert() Method

The insert() method of the StringBuilder class inserts the given string at the given position with this string.

 // Java example of String insert() Method

public class Main {	
    public static void main(String args[]){  		 
      StringBuilder sb = new StringBuilder("Exam");
      sb.insert(4,"Deva"); //  original string is now changed
      System.out.println(sb);
  } 
}

Output:

DockerTpoint

Java String delete() Method

The delete() method of the StringBuilder class remove the specified string from the begin Index and end Index.

 // Java example of String delete  Method

public class Main {	
    public static void main(String args[]){  		 
      StringBuilder sb = new StringBuilder("DockerTpoint"); 
      sb.delete(0,4);  //   original string is now changed
      System.out.println(sb);
  } 
}

Output:

Deva

Java String replace Method

The substring method of the StringBuilder class replaces the given string between begin Index and end Index-1.

 // Java example of String substring (int start, int end)  Method

public class Main {	
    public static void main(String args[]){  		 
       StringBuilder sb = new StringBuilder("E  Deva"); 
       sb.replace(1,3,"xam");  // it will replace white space, original string is now changed
      System.out.println(sb);
  } 
}

Output:

DockerTpoint

Java String reverse Method

The reverse method of the StringBuilder class reverses the current string.

 // Java example of String concat Method

public class Main {	
    public static void main(String args[]){  		 
      StringBuilder sb = new StringBuilder("DockerTpoint"); 
      sb.reverse();
      System.out.println(sb);
  } 
}

Output:

aveDmaxE

Java String capacity Method

The capacity method of the StringBuilder class returns the buffer's current capacity. The buffer's default capacity is sixteen. If the number of characters exceeds the current capacity, the capacity is increased by (oldcapacity*2)+2.

 // Java example of String indexOf Method

public class Main {	
    public static void main(String args[]){  		 
      StringBuilder sb = new StringBuilder();
      System.out.println(sb.capacity()); // default value  16
      sb.append("DockerTpoint");
      System.out.println(sb.capacity()); // capicity is 16
      sb.append("I Love India");
      System.out.println(sb.capacity()); // Now (16*2)+2=34     i.e (oldcapacity*2)+2  
  } 
}

Output:

Important methods of StringBuilder class

Important methods of StringBuilder class are mention below

Type and Modifier	Method	Description
public StringBuilder	append(String s)	Append(String s) is used to append the specified string to this string. The append() method has several overloads, including append(char), append(boolean), append(int), append(float), append(double)
public synchronized StringBuilder	insert(int value, String s)	The specific implementation of a method that is already provided by its parent class or superclass is granted by method overriding.
public synchronized StringBuilder	replace(int begin Index, int end Index-1, String str)	Replace is used to replace the string between the specified begin and end indexes.
public String	substring(int begin Index, int end Index)	substring returns the substring from the specified beginIndex and endIndex.
public String	substring(int beginIndex)	Substring returns the substring from the specified begin Index.
public int	length()	length() returns the length of the string, i.e. the total number of characters.
public char	charAt(int index)	charAt(int index) returns the character at the specified position.
public int	capacity()	capacity() returns the current capacity.
public void	ensureCapacity(int minimumCapacity)	ensureCapacity(int minimumCapacity) ensures that the capacity is at least equal to the specified minimum.
public StringBuilder	reverse()	The string can be reversed using reverse().
public StringBuilder	delete(int start Index, int end Index)	The string can be removed from the startIndex and endIndex by using the delete() method.
public void	setCharAt(int index, char c)	In setCharAt(int index, char c) method the character at the specified index is set to c.
public int	String toString()	The string returned by the string toString() method represents the data in this sequence.

Difference betweeen String and StringBuffer Next »

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Java StringBuilder Class

Class hierarchy

Important Constructors of StringBuilder Class

Important methods of StringBuilder class

Java String append() Methods

Java String insert() Method

Java String delete() Method

Java String replace Method

Java String reverse Method

Java String capacity Method

Important methods of StringBuilder class

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