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what is the Difference Between String , StringBuilder and StringBuffer Classes in java?.

Difference Between String , StringBuilder and StringBuffer Classes
Here  we are going to understand the difference between String , StringBuilder and StringBuffer . As you will find that there are minor differences between the above mentioned classes are as follows:







String is immutable ( once created can not 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 can not be used by two threads simultaneously.
String once assigned can not be changed .

String demo = " hello java " ;

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

String demo = " hi java " ;

 //new "hi java" string is created in constant pool and referenced by the demo variable
// "hello java" string still exists in string constant pool and its value is not overrided but we lost reference to the "hello java"string



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 property . Thus StringBuilder is faster than the StringBuffer when calling the same methods of each class.

StringBuffer value can be changed , it means it can be assigned to the new value . Nowadays its a most common interview question ,the differences between the above classes .
String Buffer can be converted to the string by using
toString() method.

StringBuffer test = new StringBuffer("Hello") ;

// The above object stored in heap and its value can be changed .

test=new StringBuffer("hello java");

Above statement is right as it modifies the value which is allowed in the StringBuffer


StringBuilder is same as the StringBuffer , that is it stores the object in heap and it can also be modified . The main difference between the StringBuffer and StringBuilder is that StringBuilder is also not thread safe.
StringBuilder is fast as it is not thread safe .

StringBuilder demo= new StringBuilder("Hello");
// The above object too is stored in the heap and its value can be modified

demo=new StringBuilder("hello java");
// Above statement is right as it modifies the value which is allowed in the StringBuilder

Storage Area in Constant String Pool Storage Area in heap Storage Area in heap
Modifiable  No (immutable) Yes( mutable ) Yes( mutable )
Thread Safe  Yes Thread Safe Yes Thread Safe No
 Performance Fast  Performance very slow  Performance Fast


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