Java Coding Problems

49. Writing an immutable class

An immutable class must respect several requirements, such as the following:

• The class should be marked as final to suppress extensibility (other classes cannot extend this class; therefore, they cannot override methods)
• All fields should be declared private and final (they are not visible in other classes, and they are initialized only once in the constructor of this class)
• The class should contain a parameterized public constructor (or a private constructor and factory methods for creating instances) that initializes the fields
• The class should provide getters for fields
• The class should not expose setters

For example, the following Point class is immutable since it successfully passes the preceding checklist: ...