String Builder

StringBuilder

StringBuilder object same as string objects, we use string builder instead of string for better performance.

StringBuilderConstructors are,

StringBuilder()

Creates an empty string builder with a capacity of 16 (16 empty elements).

StringBuilder(CharSequence cs)

Constructs a string builder containing the same characters as the specified CharSequence, plus an extra 16 empty elements trailing the CharSequence.

StringBuilder(int initCapacity)

Creates an empty string builder with the specified initial capacity.

StringBuilder(String s)

Creates a string builder whose value is initialized by the specified string, plus an extra 16 empty elements trailing the string.

StringBuilder Methods are,

StringBuilder append(boolean b)
StringBuilder append(char c)
StringBuilder append(char[] str)
StringBuilder append(char[] str, int offset, int len)
StringBuilder append(double d)
StringBuilder append(float f)
StringBuilder append(int i)
StringBuilder append(long lng)
StringBuilder append(Object obj)
StringBuilder append(String s)

StringBuilder delete(int start, int end)
StringBuilder deleteCharAt(int index)

StringBuilder insert(int offset, boolean b)
StringBuilder insert(int offset, char c)
StringBuilder insert(int offset, char[] str)
StringBuilder insert(int index, char[] str, int offset, int len)
StringBuilder insert(int offset, double d)
StringBuilder insert(int offset, float f)
StringBuilder insert(int offset, int i)
StringBuilder insert(int offset, long lng)
StringBuilder replace(int start, int end, String s)
void setCharAt(int index, char c)ringBuilder insert(int offset, Object obj)
StringBuilder insert(int offset, String s)

StringBuilder reverse()

String toString()

Example a program that would be more efficient if a StringBuilder were used instead of a String-

Program for reverse string using string-

public class StringReverse {
  public static void main(String[] args) {
        String myString = "I Like Java Programming";
        int len = myString.length();
        char[] tempCharArray = new char[len];
        char[] charArray = new char[len];
       
        // put original string in an
        // array of chars
        for (int i = 0; i < len; i++) {
            tempCharArray[i] =
                myString.charAt(i);
        }
       
        // reverse array of chars
        for (int j = 0; j < len; j++) {
            charArray[j] =
                tempCharArray[len - 1 - j];
        }
       
        String reverseMyString =
            new String(charArray);
        System.out.println(reverseMyString);
    }  

}

Program for reverse string using StringBuilder reverse method-

public class StringBuilder {
   public static void main(String[] args) {
        String myString = "I Like Java Programming";
        
        StringBuilder sb = new StringBuilder(myString);
       
        sb.reverse();  // reverse it
       
        System.out.println(sb);
    }

// Constructor
    private StringBuilder(String myString) {
        throw new UnsupportedOperationException("Your method not working");
    }

    // Method
    private void reverse() {
        throw new UnsupportedOperationException("Your method not working");
       
    }

}

And Output will be same in both cases-