What is mutable and immutable for string in java?

Immutable

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In java , immutable means , if we assign any value to string , means after creating an object that we can not re-assign a value to that particular staring object.

Example:

1. public class ImMutableString {
2.  
3. final String n;
4.  
5. ImMutableString(String n) {
6. this.n = n;
7. }
8.  
9. public String getN() {
10. return n;
11. }
12.  
13. // this setter can modify the name
14. public void setN(String n) {
15. this.n = n;
16. }
17.  
18. public static void main(String[] args) {
19.  
20. ImMutableString obj = new ImMutableString("Amit");
21. System.out.println(obj.getN());
22.  
23. // update the name, this object is mutable
24. obj.setName("Rahul");
25. System.out.println(obj.getN());
26.  
27. }
28. }

when we are going for print this value, we will get only output as a Amit not Rahul,

This is a concept of immutable.

mutable

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In java , mutable means , if we assign any value to StringBuffer or StringBuilder , means after creating an object that we can re-assign a value to that particular staring object.

Example:

 

1. public class MutableString {
2.  
3. private String n;
4.  
5. MutableString(String n) {
6. this.n = n;
7. }
8.  
9. public String getN() {
10. return n;
11. }
12.  
13. // this setter can modify the name
14. public void setN(String n) {
15. this.n = n;
16. }
17.  
18. public static void main(String[] args) {
19.  
20. MutableString obj = new MutableString("Amit");
21. System.out.println(obj.getN());
22.  
23. // update the name, this object is mutable
24. obj.setName("Rahul");
25. System.out.println(obj.getN());
26.  
27. }
28. }

when we are going for print this value, we will get only output as a Amit and  Rahul both,

This is a concept of mutable.

    

String object is immutable ,how?

String object is immutable ,how?

We create an object of String and initialize a value to it.
We create more than one reference variable of the same object and trying to assign a new value to it.
if we assign a value to any reference variable then value will be changed of all reference variables.
So java did not gave a permission to implement String Object in this way.