Java String is Immutable

In Java, a String object is immutable, meaning that once it is created, its contents cannot be changed. This means that any changes to a String object result in the creation of a new String object.

This behavior of String objects being immutable is by design, and has several benefits. It makes String objects thread-safe, which means that multiple threads can access a String object without the risk of unexpected changes. It also allows for better memory management, as immutable objects can be cached and reused without having to worry about their contents changing.

Let’s take a look at an example to see how String immutability works in practice:

String s1 = "Hello";
String s2 = s1;

s1 = s1 + " World";

In the above code, we create two String objects, s1 and s2, both containing the string “Hello”. We then modify s1 by concatenating the string ” World” to it. However, this does not change the value of s2, which still contains the original string “Hello”. Instead, a new String object is created with the value “Hello World”, and s1 now references this new object.

This immutability of String objects means that any operations that modify the contents of a String object, such as concatenation or substring operations, will result in the creation of a new String object. This can have performance implications if these operations are performed frequently on large String objects.

In conclusion, understanding the immutability of String objects in Java are important for writing efficient and safe code. It is important to keep in mind that any modifications to a String object result in the creation of a new object, and to use the appropriate data structures and algorithms to optimize performance when working with String objects.