String Vs StringBuffer in Java

Last Updated: 22 January, 2023

String and StringBuffer are final classes of the java.lang package and are used to store a sequence of characters.

There are many differences between the String and StringBuffer that are given below.

👉 String

A String is an immutable and final class in Java. It was introduced in the JDK 1.0 version and defined in the java.lang package.

Java String is an object that allows us to store a sequence of characters. A string object may contain any type of data, such as alphanumeric, special characters, blank spaces, etc., values enclosed in double quotes.

For example, "Core Java" is a string containing a sequence of characters 'C', 'o', 'r', 'e', 'J', 'a', 'v' and 'a'.

Strings are immutable in Java which means their values cannot be changed once they are created; if we modify the string, the JVM will create a new object. 

String Class Description

public final class String
extends Object
implements Serializable, Comparable<String>, CharSequence

• String is not a primitive data type like int and long, etc.
• The default value of the String variable is null.
• In Java, only the String class supports operator overloading. Using the + operator, we can concatenate two strings. For example, "Core" + "Java" = "Core Java".
• The String class provides many methods to perform certain operations on strings, such as length(), replace(), substring(), etc.

In Java, there are two ways to create a String object.

1. By string literal

A Java String literal is created by using double quotes.
For example:

String str = “Hello Java”;

2. Using a new keyword

The "new" keyword is used to create a Java String.
For example:

String str = new String(“Hello Java”);

Java String Example

public class StringExample { public static void main(String[] args) { // Creating Strings by literals String str1 = "Hello"; String str2 = "Hello Java"; String str3 = "Hello"; // Creating Strings by 'new' keyword String s1 = new String("Java World"); String s2 = new String("Hello Java"); System.out.println("str1 value: " + str1); System.out.println("str2 value: " + str2); System.out.println("str3 value: " + str3); System.out.println("s1 value: " + s1); System.out.println("s2 value: " + s2); } }

Output

str1 value: Hello
str2 value: Hello Java
str3 value: Hello
s1 value: Java World
s2 value: Hello Java

When we create a String by literal, the object is always created inside the String pool, whereas if we create a string object using the 'new' keyword, it will be created inside the heap memory area.

👉 StringBuffer

StringBuffer is a mutable, final, and synchronized (thread-safe) Java class that was introduced in the JDK 1.0 version and is available in the java.lang package.

The StringBuffer class is used to create a mutable String object (the object can be changed once created). StringBuffer is similar to the String class except for one major difference: StringBuffer is mutable, whereas String is immutable (an object cannot be changed once it is created).

The StringBuffer class is thread-safe, which means that at any time, multiple threads cannot access it simultaneously. So it is safe and will result in order, but implementing the synchronization mechanism will take some time for the JVM, which is why StringBuffer is a little slower than StringBuilder.

Java StringBuffer Class Declaration

public final class StringBuffer
extends Object
implements Serializable, Comparable <StringBuffer>, CharSequence

Example: A sample Java program of StringBuffer

public class StringBufferDemo { public static void main(String[] args) { StringBuffer buffer = new StringBuffer("Welcome in StringBuffer Class"); System.out.println(buffer); } }

Output

Welcome in StringBuffer Class

👉 String and StringBuffer have the following differences: