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In computer programming, field encapsulation involves providing methods that can be used to read from or write to the field rather than accessing the field directly. Sometimes these accessor methods are called ''getX'' and ''setX'' (where X is the field's name), which are also known as mutator methods. Usually the accessor methods have public visibility while the field being encapsulated is given private visibility - this allows a programmer to restrict what actions another user of the code can perform. Compare the following Java class in which the ''name'' field has not been encapsulated: public class NormalFieldClass } with the same example using encapsulation: public class EncapsulatedFieldClass public static void main(String[] args) } In the first example a user is free to use the public ''name'' variable however they see fit - in the second however the writer of the class retains control over how the private ''name'' variable is read and written by only permitting access to the field via its ''getName'' and ''setName'' methods. ==Advantages== *The internal storage format of the data is hidden; in the example, an expectation of the use of restricted character sets could allow data compression through recoding (e.g., of eight bit characters to a six bit code). An attempt to encode characters out of the range of the expected data could then be handled by casting an error in the ''set'' routine. *In general, the ''get'' and ''set'' methods may be produced in two versions - an efficient method that assumes that the caller is delivering appropriate data and that the data has been stored properly, and a debugging version that while slower, performs validity checks on data received and delivered. Such detection is useful when routines (calling or called) or internal storage formats are newly created or modified. *The location of the stored data within larger structures may be hidden and so enabling changes to be made to this storage without the necessity of changing the code that references the data. This also reduces the likelihood of unexpected side effects from such changes. This is especially advantageous when the accessors are part of an operating system (OS), a case where the calling (application) code may not be available to the developers of the OS. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Field encapsulation」の詳細全文を読む スポンサード リンク
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