1.重構

（1）重構變量

• Shift+F6 批量重命名變量(Rename)

• private String bcd;//光標在bcd處，按Shift+F6，改為lastname
  
  public String getFullName(String abc){//光標在abc處，按Shift+F6，改為firstname
      System.out.println("your firstname: "+abc);
      System.out.println("your lastname: "+this.bcd);
      String fullName=abc+this.bcd;
      System.out.println("your fullname: "+fullName);
  
      this.sayHello(abc);
      return fullName;
  }
• 這段代碼abc,bcd含義不明，將abc重構為firstname，bcd重構為lastname，提高代碼可讀性，改為如下

• private String lastname;
  
  public String getFullName(String firstname){
      System.out.println("your firstname: "+firstname);
      System.out.println("your lastname: "+this.lastname);
      String fullName=firstname+this.lastname;
      System.out.println("your fullname: "+fullName);
  
      this.sayHello(firstname);
      return fullName;
  }

（2）重構方法

• 方法一： Ctrl+F6 改變方法 (change signature)

• public String getFullName(String firstname){
      //
      this.sayHello(firstname);//2.此處出現紅波浪，手動添加,lastname
      //
  }
  private void sayHello(String firstname) {//1.在此處按Ctrl+F6 ,即出現一個彈框,在裏面點+，輸入String lastname即可
      
  }

• 方法二：Ctrl+Alter自動修改

• public String getFullName(String firstname){
      //
      this.sayHello(firstname);//1.此處添加,lastname，按下Alt+Enter,選擇Add String as 2nd parameter to method sayHello
      //
  }
  private void sayHello(String firstname) {//2.此處自動變為private void sayHello(String firstname, String lastname)

      
  }

2.抽取

（1）抽取變量

• Ctrl+Alt+v 抽取變量(extract variable)，v就相當於variable

• public void foo(){
      getFullname("san");//光標放在san上，Ctrl+Alt+v， replace all 6 occurrebces
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
  }

• 代碼多次需要用到“san”變量，我們可以把它抽取出來,變為

• public void foo(){
      String lastname = "san";
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
  }

（2）抽取靜態變量

• Ctrl+Alt+c 抽取靜態變量(extract constant)，c就相當於constant

• public void foo(){
      getFullname("san");//光標放在san上，Ctrl+Alt+c， replace all 6 occurrebces
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
  }

• 代碼多次需要用到“san”作為靜態變量，我們可以把它抽取出來,變為

• public static final String LASTNAME = "san";
  
  public void foo(){
      getFullname(LASTNAME);
      getFullname(LASTNAME);
      getFullname(LASTNAME);
      getFullname(LASTNAME);
      getFullname(LASTNAME);
      getFullname(LASTNAME);
  }

（3）抽取成員變量

• Ctrl+Alt+f 抽取成員變量(extract field)，f就相當於field

• public void foo(){
      getFullname("san");//光標放在san上，Ctrl+Alt+f， replace all 6 occurrebces
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
      getFullname("san");
  }

• 代碼多次需要用到“san”作為靜態變量，我們可以把它抽取出來,變為

• private String lastname;
  
  public void foo(){
      lastname = "san";
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
      getFullname(lastname);
  }

（4）抽取方法參數

• Ctrl+Alt+p 抽取方法參數(extract parameter)，p就相當於parameter

• private String firstName;
  
  private String getFullname(String lastName) {
      String fullName= this.firstName +","+lastName;//光標放在firstName，Ctrl+Alt+p
      return fullName;
  }
  
  public void foo(){
      getFullname("san");
  }

• 將firstName它抽取出來,就可以將getFullname()抽取出來成為一個服務，放到別的類裏面都可以，變為

• private String firstName;
  
  private String getFullname(String lastName, String firstName) {
      String fullName= firstName +","+lastName;
      return fullName;
  }
  
  public void foo(){
      getFullname("san", this.firstName);
  }

（5）抽取函數

• Ctrl+Alt+m 抽取函數(extract method)，m就相當於method

• public void foo(){
      step1();
      step2();//選中他倆，按Ctrl+Alt+m，在彈框中輸入validate
  
      step3();
      step4();//選中他倆，按Ctrl+Alt+m，在彈框中輸入loadDataFromDB

      step5();
      step6();//選中他倆，按Ctrl+Alt+m，在彈框中輸入calc

  }

• public void foo(){
      validate();//校驗參數
      loadDataFromDB();//數據庫加載數據
      calc();//邏輯運算
  }
  
  private void calc() {
      step5();
      step6();
  }
  
  private void loadDataFromDB() {
      step3();
      step4();
  }
  
  private void validate() {
      step1();
      step2();
  }

代碼重構