Immutable Objects in java
Wed, Nov 20, 2019
Read in 1 minutes
What is immutable?
If you cannot change the content of the object, then that is called immutable objects. String and all other wrapper classes Integer, Double are immutable.
How to create custom immutable objects?
- Create final class. So that it cannot be overridden by a subclass.
- Declare all the data members as private final. So that the class members cannot be assigned to a new value.
- Don’t write any setter methods.
public final class CreditCard {
private final Long cardNumber;
private final String cardHolderName;
public CreditCard(Long cardNumber, String cardHolderName) {
super();
this.cardNumber = cardNumber;
this.cardHolderName = cardHolderName;
}
public Long getCardNumber() {
return cardNumber;
}
public String getCardHolderName() {
return cardHolderName;
}
public static void main(String[] args) {
CreditCard card= new CreditCard(1243536L, "rty");
System.out.println(card.cardHolderName);
System.out.println(card.cardNumber);
//card.cardHolderName="xxxx";
}
}
If you try a change the content of the object, you will get below error.
So, If you want to change the content fo the object, you have to create a new object.