重構之2.Replace Type Code with Class(以類取代類型碼)，2.replacecode

重構之2.Replace Type Code with Class(以類取代類型碼)，2.replacecode
情境

在一個類中我們經常會下定義一些類型碼，如:

public static final int INVALID=0;public static final int VALID=1;

我們可以將這些數值轉換為一個類

前提條件:

只有當類型碼是純粹資料時（類型碼不會在Switch語句中引起行為的變化時），你才能以類來取代它

修改前代碼:

Student

package com.demo.refactor.codetype.before;public class Student {private int id;private String name;/** *狀態:0,有效,1無效  */private int status ;public static final int INVALID=0;public static final int VALID=1;public Student(int id, String name, int status) {super();this.id = id;this.name = name;this.status = status;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getStatus() {return status;}public void setStatus(int status) {this.status = status;}@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + ", status=" + status+ "]";}}

test:

package com.demo.refactor.codetype.before;public class StudentTest {/** * @param args */public static void main(String[] args) {Student student=new Student(1, "張三", Student.VALID);System.out.println(student);}}

修改後:

StatusCode

package com.demo.refactor.codetype.after;public class StatusCode {public static final StatusCode invalid=new StatusCode(0);public static final StatusCode valid=new StatusCode(1);public static final StatusCode[] codes={invalid,valid};private int code;private StatusCode(int code) {this.code = code;}/** * @param index  * @return */public static StatusCode create(int index){return codes[index];}public int getCode() {return code;}public void setCode(int code) {this.code = code;}@Overridepublic String toString() {return "StatusCode [code=" + code + "]";}}

Student

package com.demo.refactor.codetype.after;public class Student {private int id;private String name;private StatusCode code;public Student(int id, String name, StatusCode code) {this.id = id;this.name = name;this.code = code;}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getCode() {return code.getCode();}public void setCode(int index) {this.code =StatusCode.create(index);}@Overridepublic String toString() {return "Student [id=" + id + ", name=" + name + ", code=" + code + "]";}}

StudentTest

package com.demo.refactor.codetype.after;public class StudentTest {/** * @param args */public static void main(String[] args) {Student stu=new Student(1, "李四", StatusCode.invalid);System.out.println(stu);}}