StringBuffer in Java Programming
String in Java
In this lesson, we will understand what is StringBuffer in Java Programming along with some examples.
What is StringBuffer in Java
A StringBuffer is a class in java which is used to store a thread-safe, mutable sequence of characters. A StringBuffer is like a String, but can be modified.
Syntax of Creating a StringBuffer Object
StringBuffer object_name=new StringBuffer("string value");Example
StringBuffer sb=new StringBuffer("Dremendo");Here we have declared a StringBuffer object sb and initialize it with the string value Dremendo.
Methods of StringBuffer Class
StringBuffer methods are useful functions used to perform a specific task on the content of the StringBuffer object. Below we have discussed all the important StringBuffer methods available in the StringBuffer class.
length() Method
The length() method returns the total number of characters (including space) present in the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
int l;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
l=sb.length();
System.out.println("Length="+l);
}
}Output
Enter a string Hello World Length=11
charAt() Method
The charAt() method returns the character at the specified index. In a string buffer object, the first character starts from index 0.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
int l;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
System.out.println("Character at index 3="+sb.charAt(3));
}
}Output
Enter a string Dremendo Character at index 3=m
setCharAt() Method
The setCharAt() method set a specified character at the specified index in the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
sb.setCharAt(2,'m');
System.out.println(sb);
}
}Output
Enter a string Tiger Timer
deleteCharAt() Method
The deleteCharAt() method removes a character at the specified index in the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
sb.deleteCharAt(2);
System.out.println(sb);
}
}Output
Enter a string Tiger Tier
delete() Method
The delete() method removes character sequences from the specified start index till end index-1 in a string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
sb.delete(1,5);
System.out.println(sb);
}
}Output
Enter a string Computer Cter
indexOf() Method
The indexOf() method returns the index of the first occurrence of the specified character or string within the current string buffer object. The indexOf() method accepts two arguments. The first argument is the string or character and the second optional argument is the index from where we want to check the occurrence. If the index is not given, it will start checking the occurrence from index 0.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
s1=sc.nextLine();
s2=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
System.out.println("The 2nd string first occur at index " + sb.indexOf(s2) + " in the string buffer object.");
System.out.println("After index 5, the 2nd string first occur at index " + sb.indexOf(s2,5) + " in the string buffer object.");
}
}Output
Enter 2 strings I am a boy and I love java programming. I The 2nd string first occur at index 0 in the string buffer object. After index 5, the 2nd string first occur at index 15 in the string buffer object.
lastIndexOf() Method
The lastIndexOf() method returns the index of the last occurrence of the specified character or string within the current string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
s1=sc.nextLine();
s2=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
System.out.println("The 2nd string last occur at index " + sb.lastIndexOf(s2) + " in the string buffer object.");
}
}Output
Enter 2 strings I am a boy and I love playing football. I The 2nd string last occur at index 15 in the string buffer object.
toString() Method
The toString() method returns a string representing the data of the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s1=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
s2=sb.toString();
System.out.println(s2);
}
}Output
Enter a string Java Programming Java Programming
append() Method
The append() method appends the specified string to the end of the current string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
s1=sc.nextLine();
s2=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
sb.append(s2);
System.out.println(sb);
}
}Output
Enter 2 strings good bye goodbye
replace() Method
The replace() method replaces a substring with the specified string in the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
s1=sc.nextLine();
s2=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
sb.replace(7,13,s2);
System.out.println(sb);
}
}Output
Enter 2 strings I Love Orange Apple I Love Apple
insert() Method
The insert() method insert a specified string in the string buffer object at the specified index.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s1,s2;
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
s1=sc.nextLine();
s2=sc.nextLine();
StringBuffer sb=new StringBuffer(s1);
sb.insert(0,s2);
System.out.println(sb);
}
}Output
Enter 2 strings how are you Hello Hello how are you
reverse() Method
The reverse() method replaces the character sequence of the string buffer object by the reverse of the sequence.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
sb.reverse();
System.out.println(sb);
}
}Output
Enter a string Apple elppA
substring() Method
The substring() method returns a new string which is a substring currently contained in the string buffer object.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
String s;
Scanner sc=new Scanner(System.in);
System.out.println("Enter a string");
s=sc.nextLine();
StringBuffer sb=new StringBuffer(s);
System.out.println("Print the 1st 3 characters of the current string");
System.out.println(sb.substring(0,3));
System.out.println("Print the 1st 3 characters starting from index 2 and stopping at index 5");
System.out.println("The stopping index is not included in the substring");
System.out.println(sb.substring(2,5));
System.out.println("Print all the characters starting from index 3 till end");
System.out.println(sb.substring(3));
}
}Output
Enter a string Dremendo Print the 1st 3 characters of the current string Dre Print the 1st 3 characters starting from index 2 and stopping at index 5 The stopping index is not included in the substring eme Print all the characters starting from index 3 till end mendo
How to compare the data of two string buffer objects?
To compare the data of two string buffer object, first, we have to convert their data into the string and then apply the compareTo() or compareToIgnoreCase() function of the String class on it. Let's see the example given below.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
System.out.println("Enter 2 strings");
StringBuffer sb1=new StringBuffer(sc.nextLine());
StringBuffer sb2=new StringBuffer(sc.nextLine());
if(sb1.toString().compareTo(sb2.toString())==0)
{
System.out.println("Both the strings are same");
}
else
{
System.out.println("Both the strings are not same");
}
}
}Output
Enter 2 strings Computer Computer Both the strings are same
How to overwrite a string buffer object with a new string?
To overwrite a string buffer object with a new string, we have to replace the old string with the new one. Let's see the example given below.
Example
import java.util.Scanner;
public class StringBufferMethod
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
String s;
System.out.println("Enter 2 strings");
StringBuffer sb=new StringBuffer(sc.nextLine());
s=sc.nextLine();
System.out.println("Current string in string buffer object = " + sb);
sb.replace(0,sb.length(),s);
System.out.println("New string in string buffer object = " + sb);
}
}Output
Enter 2 strings Apple Ball Current string in string buffer object = Apple New string in string buffer object = Ball
