How to create an immutable class which contains date object

Some time you may need to write immutable class which includes mutable classes like java.util.Date, despite storing Date into final field it can be modified internally, if internal date is returned to the client. In order to preserve immutability in such cases, its advised to return copy of original object, which is also one of the Java best practice. here is another example of making a class immutable in Java, which includes mutable member variable.

public final class ImmutableReminder{
    private final Date remindingDate;
 
    public ImmutableReminder (Date remindingDate) {
        if(remindingDate.getTime() < System.currentTimeMillis()){
            throw new IllegalArgumentException("Can not set reminder” +
                        “ for past time: " + remindingDate);
        }
        this.remindingDate = new Date(remindingDate.getTime());
    }
 
    public Date getRemindingDate() {
        return (Date) remindingDate.clone();
    }
}
 
 
Read more: http://javarevisited.blogspot.com/2013/03/how-to-create-immutable-class-object-java-example-tutorial.html#ixzz58Qr9uwhZ

Uday Ogra

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