Why Are Strings Immutable In Java? Know The Actual Reason!

Hey everyone, in this video we talked about the reason behind strings are immutable in Java. This is one of the popular Java interview questions and also asked as to why String is final in Java. In this video, we will answer this Java interview question with details and examples.

Before proceeding further with the fuss of immutability, let’s just take a look into the String class and its functionality a little before coming to any conclusion.

This is how String works:

String str = "knowledge";
This, as usual, creates a string containing "knowledge" and assigns it to reference str. Simple enough? Let's perform some more functions:

// assigns a new reference to the
// same string "knowledge"
String s = str;
Let’s see how the below statement works:

This appends a string " base" to str. But wait, how is this possible, since String objects are immutable? Well to your surprise, it is.

When the above statement is executed, the VM takes the value of String str, i.e. "knowledge" and appends " base", giving us the value "knowledge base". Now, since Strings are immutable, the VM can’t assign this value to str, so it creates a new String object, gives it a value "knowledge base", and gives it a reference str.

An important point to note here is that, while the String object is immutable, its reference variable is not. So that’s why, in the above example, the reference was made to refer to a newly formed String object.

At this point in the example above, we have two String objects: the first one we created with value "knowledge", pointed to by s, and the second one "knowledge base", pointed to by str. But, technically, we have three String objects, the third one being the literal "base" in the concat statement.

[vishnunatarajan]

i have been come through so many videos .i could understood the string immutability concept by watching your videos.thank you

[saransinha]

jab har baar string change hi ho rahi hai to immutabel kyon?

[rohitmalhotra]

So, does security is the only reason for String being Immutable?

[DeepakTiwari-iply]

is this channel belongs to Javin Paul? Came here with lot of expectations as I am following his blog for last 4-5 years. But this YouTube channel disappointed me.

[tejap]

You need to practice more and explain better. Few times you are not able to explain clearly.