Guide to String Class in Java development - Blog for Software and Technology

In the world of the internet, the data’s which use to get communicated from one source to another are more basic in the form of strings.

In terms of Java, there is a class called String. It is one of the important topics in terms of core java.

Today in this blog, we will discuss String class, its immutability, why java people have made the String class is immutable and as well as how to design the immutable class in java. Then a simple comparison of StringBuffer and StringBuilder class. And last we will see what String pool is.

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So, first of all, let’s list down the topics below:

String Class concept and its immutability concept. Why and How.
Comparison of StringBuffer and StringBuilder classes. Why they introduced.
How to design an immutable class in java.
What is the String pool?

Let’s get started.

String:

In java String is a class introduced in the package named as java.lang. The string represents a group of characters.

We can instantiate a String in two ways

String name = “Ankit Jaiswal”; and String name = new String(“Ankit Jaiswal”);

When we create String using double quotes, it first looks for the String with the same value in the JVM String pool, if the String is found then the reference is returned else it creates, the String object and then places it in the String pool.

String overrides equals() and hashCode() method of the Object class, two Strings are equal only if they have the same characters in the same order.

What are Immutable Objects in Java?

Ans: Immutable objects are those objects that don’t change. You make them, then you can’t change them. If you want to change an immutable object you have to clone the immutable object then, change the cloned object

Why Java People have designed String as an immutable class?

Ans: Java people have designed the string as a variable class in Java because String objects are cached in the string pool. Since cached String literals are shared among multiple clients, there is always a risk, where the actions of one client will affect all other clients. For example, if the value of a client string "numbered" changes to "numbered," all clients will see that value. Since caching of string performance objects is important for a performance perspective, this was avoided by making string objects unchangeable. String class was made final too as to stop the extending of class and finally changing the values of the String object created indirectly. Which is called an invariant concept?

Steps to design immutable class in java:

Create a class and make a class final, so that the class cannot be incremented.
Make all fields private so that no direct allowed access is allowed.
Finalize all variable areas. So that its values are assigned only once.
Define the constructor of the parameters with the declared variables. Accessors must be public.
Do not provide setter methods for variables.
Clone the objects in the getter method to return the copy instead of returning the actual object reference.

Code example:

StringBuffer and StringBuilder classes and their comparison

StringBuffer and StringBuilder classes are used when many changes to the string of strings are required.

If we compare StringBuffer and StringBuilder objects with a String object then it is changeable. So that they can be fixed again and again without leaving too many unused behind objects.

The StringBuilder class was introduced in Java Web Development. And the main difference between StringBuffer and StringBuilder is that StringBuilder methods do not thread securely.

It is recommended to use String Builder as it is faster than StringBuffer. If thread protection is necessary, then we can go with StringBuffer.

What is String Pool?

Ans: String Pool is a cache mechanism designed to come up with performance risk. As we all aware that String is one of the most widely used in java. Almost in every class. So whenever we create a String with double-quotes. So the first operation used to search JVM cache named as String pool with the same values created with the double quotes if found the reference of the String will be returned or else a new String will be created with a different reference.

If a String is created with a new keyword string pool will never be scanned and instead of that, a new object will be created with a reference variable assigned to it.

Conclusion:

So the almost conclusion of this topic is that String is one of the widely used classes in java.

And as it is so widely used it should be cached in the string pool of the JVM memory, so that the performance can be increased.

But since the object is cached it is on the high risk to get changed often when multiple clients access it. So to overcome that String class was made as immutable.