Java Immutable Classes

• What is an immutable class

1. When you obtain a reference to this class, you cannot change the contents of this class;
2. Once an instance of an immutable class is created, its member variables cannot be modified;

　　

• How to create immutable classes

1. Member variables are private permissions
2. does not provide an external interface that alters member variables, that is, the Set method
3. All methods are not overloaded and are implemented in two ways: 1) All methods plus the final keyword (weakly immutable Class) 2) Use final class (strong non-volatile class)
4. If the member variable of the class is a variable subclass, then in the initialization process, the variable subclass needs to be deeply copied;

Example:

1  Public classImmutedemo {2     PrivateString name;//String is an immutable class3     PrivateDate date;//Date is a mutable class4 5      PublicImmutedemo (String name,date Date) {6          This. Name =name;7          This. Date =NewDate (Date.gettime ());//Copy the input object8    //date.settime (2101); Changes the input object without affecting the value of the member date9     }Ten  One      PublicString GetName () { A         returnname; -     } -  the      PublicDate getDate () { -         return NewDate (Date.gettime ()); -     } -  +      Public Static voidMain (string[] args) { -Date Date =NewDate (); +Immutedemo Immutedemo =NewImmutedemo ("Zhang San", date); A     } at } -  　　 

Java Immutable Classes