Why is String immutable in Java?

Question

I was asked in an interview why String is immutable

I answered like this:

When we create a string in java like String s1="hello"; then an object will be created in string pool(hello) and s1 will be pointing to hello.Now if again we do String s2="hello"; then another object will not be created but s2 will point to hello because JVM will first check if the same object is present in string pool or not.If not present then only a new one is created else not.

Now if suppose java allows string mutable then if we change s1 to hello world then s2 value will also be hello world so java String is immutable.

Can any body please tell me if my answer is right or wrong?

Answer 1

Java Developers decide Strings are immutable due to the following aspect design, efficiency, and security.

Design Strings are created in a special memory area in java heap known as "String Intern pool". While you creating new String (Not in the case of using String() constructor or any other String functions which internally use the String() constructor for creating a new String object; String() constructor always create new string constant in the pool unless we call the method intern()) variable it searches the pool to check whether is it already exist. If it is exist, then return reference of the existing String object. If the String is not immutable, changing the String with one reference will lead to the wrong value for the other references.

According to this article on DZone: