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How can we create a immutable class in Java?
To create an immutable class in Java, you have to do the following steps.
- Declare the class as final so it can’t be extended.
- Make all fields private so that direct access is not allowed.
- Don’t provide setter methods for variables.
- Make all mutable fields final so that its value can be assigned only once.
How a class can be made immutable?
In order to create an immutable class, you should follow the below steps: Make your class final, so that no other classes can extend it. Make all your fields final, so that they’re initialized only once inside the constructor and never modified afterward. Don’t expose setter methods.
Can we create object for immutable class in Java?
Immutable class in java means that once an object is created, we cannot change its content. In Java, all the wrapper classes (like Integer, Boolean, Byte, Short) and String class is immutable. We can create our own immutable class as well. The class must be declared as final so that child classes can’t be created.
Why do we create immutable class in Java?
Immutable classes make sure that values are not changed in the middle of an operation without using synchronized blocks. By avoiding synchronization blocks, you avoid deadlocks. And since you are always working with an unchangeable consistent state, you avoid race conditions.
How can we create immutable class if there is some mutable object in class?
If you want to encapsulate a mutable object into an immutable one, then you need to:
- Create a copy of the mutable object (i.e. via copy constructor, cloning, serialization/deserialization, etc.); never store the reference to the original mutable object.
- If you must to, then return a copy of the object.
What is a mutable class in Java?
The mutable objects are objects whose value can be changed after initialization. We can change the object’s values, such as field and states, after the object is created. For example, Java. util. Date, StringBuilder, StringBuffer, etc.
How can we create singleton class in Java?
To create the singleton class, we need to have static member of class, private constructor and static factory method.
- Static member: It gets memory only once because of static, itcontains the instance of the Singleton class.
- Private constructor: It will prevent to instantiate the Singleton class from outside the class.
What if immutable class contains mutable object in Java?
Immutable class is a class which once created, it’s content can not be changed. Immutable classes are good choice for HashMap key as their state cannot be changed once they are created.
What is mutable and immutable in Java?
A mutable object can be changed after it’s created, and an immutable object can’t. Strings are immutable in Java. …
How do you make an object mutable in java?
Declare the class as final so it can’t be extended. Make all fields private so that direct access is not allowed. Do not provide setter methods (methods that modify fields) for variables, so that it can not be set. Make all mutable fields final so that their values can be assigned only once.
What is mutable and immutable classes in java?
The mutable objects can be changed to any value or state without adding a new object. Whereas, the immutable objects can not be changed to its value or state once it is created. In the case of immutable objects, whenever we change the state of the object, a new object will be created.
Is Singleton class immutable?
A singleton can be mutable or immutable; a non-singleton can be mutable or immutable. However, a singleton must be thread-safe if used in multiple threads; immutable objects are inherently thread-safe.