No.	String	StringBuffer
1)	String class is immutable.	StringBuffer class is mutable.
2)	String is slow and consumes more memory when you concat too many strings because every time it creates new instance.	StringBuffer is fast and consumes less memory when you cancat strings.
3)	String class overrides the equals() method of Object class. So you can compare the contents of two strings by equals() method.	StringBuffer class doesn’t override the equals() method of Object class.

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Table of Contents

Performance Test of String and StringBuffer

1. public class ConcatTest{ 
2. public static String concatWithString() { 
3. String t = "Java"; 
4. for (int i=0; i<10000; i++){ 
5. t = t + "Tpoint"; 
6. } 
7. return t; 
8. } 
9. public static String concatWithStringBuffer(){ 
10. StringBuffer sb = new StringBuffer("Java"); 
11. for (int i=0; i<10000; i++){ 
12. sb.append("Tpoint"); 
13. } 
14. return sb.toString(); 
15. } 
16. public static void main(String[] args){ 
17. long startTime = System.currentTimeMillis(); 
18. concatWithString(); 
19. System.out.println("Time taken by Concating with String: "+(System.currentTimeMillis()-startTime)+"ms"); 
20. startTime = System.currentTimeMillis(); 
21. concatWithStringBuffer(); 
22. System.out.println("Time taken by Concating with StringBuffer: "+(System.currentTimeMillis()-startTime)+"ms"); 
23. } 
24. }

Time taken by Concating with String: 578ms
Time taken by Concatingwith StringBuffer: 0ms

String and StringBufferHashCode Test

As you can see in the program given below, String returns new hashcode value when you concat string but StringBuffer returns same.

1. public class InstanceTest{ 
2. public static void main(String args[]){ 
3. System.out.println("Hashcode test of String:"); 
4. String str="java"; 
5. System.out.println(str.hashCode()); 
6. str=str+"tpoint"; 
7. System.out.println(str.hashCode()); 
8. 
9. System.out.println("Hashcode test of StringBuffer:"); 
10. StringBuffer sb=new StringBuffer("java"); 
11. System.out.println(sb.hashCode()); 
12. sb.append("tpoint"); 
13. System.out.println(sb.hashCode()); 
14. } 
15. }

Hashcode test of String:
3254818
229541438
Hashcode test of StringBuffer:
118352462
118352462

Difference between StringBuffer and StringBuilder

Java provides three classes to represent a sequence of characters: String, StringBuffer, and StringBuilder. The String class is an immutable class whereas StringBuffer and StringBuilder classes are mutable. There are many differences between StringBuffer and StringBuilder. The StringBuilder class is introduced since JDK 1.5.
A list of differences between StringBuffer and StringBuilder are given below:

No.	StringBuffer	StringBuilder
1)	StringBuffer is synchronized i.e. thread safe. It means two threads can’t call the methods of StringBuffer simultaneously.	StringBuilder is non-synchronized i.e. not thread safe. It means two threads can call the methods of StringBuilder simultaneously.
2)	StringBuffer is less efficient than StringBuilder.	StringBuilder is more efficient than StringBuffer.

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StringBuffer Example

1. //Java Program to demonstrate the use of StringBuffer class. 
2. public class BufferTest{ 
3. public static void main(String[] args){ 
4. StringBuffer buffer=new StringBuffer("hello"); 
5. buffer.append("java"); 
6. System.out.println(buffer); 
7. } 
8. }

hellojava

StringBuilder Example

1. //Java Program to demonstrate the use of StringBuilder class. 
2. public class BuilderTest{ 
3. public static void main(String[] args){ 
4. StringBuilder builder=new StringBuilder("hello"); 
5. builder.append("java"); 
6. System.out.println(builder); 
7. } 
8. }

hellojava

Performance Test of StringBuffer and StringBuilder

Let’s see the code to check the performance of StringBuffer and StringBuilder classes.

1. //Java Program to demonstrate the performance of StringBuffer and StringBuilder classes. 
2. public class ConcatTest{ 
3. public static void main(String[] args){ 
4. long startTime = System.currentTimeMillis(); 
5. StringBuffer sb = new StringBuffer("Java"); 
6. for (int i=0; i<10000; i++){ 
7. sb.append("Tpoint"); 
8. } 
9. System.out.println("Time taken by StringBuffer: " + (System.currentTimeMillis() - startTime) + "ms"); 
10. startTime = System.currentTimeMillis(); 
11. StringBuilder sb2 = new StringBuilder("Java"); 
12. for (int i=0; i<10000; i++){ 
13. sb2.append("Tpoint"); 
14. } 
15. System.out.println("Time taken by StringBuilder: " + (System.currentTimeMillis() - startTime) + "ms"); 
16. } 
17. }

Time taken by StringBuffer: 16ms
Time taken by StringBuilder: 0ms

So, this brings us to the end of blog. This Tecklearn ‘String Vs StringBuffer Vs StringBuilder’ blog helps you with commonly asked questions if you are looking out for a job in Java Programming. If you wish to learn Java and build a career Java Programming domain, then check out our interactive, Java and JEE Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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