Difference Between String, StringBuilder And StringBuffer Classes in Java

Here we will explain the difference between String , StringBuilder and StringBuffer . As you will find that there are minor differences between the above mentioned classes.

String

• String is immutable( once created cannot be changed ) object.
• The object created as a String is stored in the Constant String Pool
• Every immutable object in Java is thread safe, that implies String is also thread safe.
• String cannot be used by two threads simultaneously.
• String once assigned cannot be changed.

Example

String  demo = " hello " ;

// The above object is stored in constant string pool and its value cannot be modified.

demo = "Bye" ;     //new "Bye" string is created in constant pool and referenced by the demo variable 

// "hello" string still exists in string constant pool and its value is not overridden but we lost reference to the "hello" string

StringBuffer 

• StringBuffer is mutable means one can change the value of the object .
• The object created through StringBuffer is stored in the heap . - StringBuffer has the same methods as the StringBuilder , but each method in StringBuffer is synchronized that is StringBuffer is thread safe.

Due to this it does not allow two threads to simultaneously access the same method. Each method can be accessed by one thread at a time.

But being thread safe has disadvantages too as the performance of the StringBuffer hits due to thread safe propert . Thus StringBuilder is faster than the StringBuffer when calling the same methods of each class.

String Buffer can be converted to the string by using toString() method.

Example:

StringBuffer demo1 = new StringBuffer("Hello") ;
// The above object stored in heap and its value can be changed.
demo1=new StringBuffer("Bye")
demo1=demo1.append("See You");
If you print demo1 you will get "HelloByeSee You"

StringBuilder 

• StringBuilder is same as the StringBuffer , i.e. the object is stored in heap and it can also be modified.
• The main difference between the StringBuffer and StringBuilder is that StringBuilder is also not thread safe. It have all the methods of StringBuffer - StringBuilder is fast as it is not thread safe.

	String	StringBuffer	StringBuilder
Storage	Constant String Pool	Heap	Heap
Mutable	No	Yes	Yes
Thread Safe	Yes	Yes	No
Performance	Fast	Slow	Fast

Hope you guys like it. Let me now in comments if you guys have any doubts. Happy Learning !!!

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