爪哇 - 如何實現方法克隆爲基礎，派生類

Question

我有三類：

類的

Base extends Object 

Derived1 extends Base 

Derived2 extends Derived1 

每個人都有自己的字段應該被克隆。我在理解實現clone的最佳方式時遇到麻煩，並避免重複代碼。我有以下架構，但看起來對我來說最差

Derived2.clone()：它調用super.clone()並收到Derived1的對象。然後它調用新的Derived2(objOfDerived1)，其調用super(objOfDerived1)，其複製其所有字段，然後在Derived2.clone()中複製Derived2的所有字段。

你會怎麼說呢？也許有任何文章描述這個問題？

UPD：這個想法在這裏可以

class Base implements Cloneable { 
    private String dataOfBase; 

    public Base() { 

    } 

    public Base(Base base) { 
     this.dataOfBase = base.dataOfBase; 
    } 

    @Override 
    public Object clone() { 
     Base base = new Base(); 
     base.dataOfBase = dataOfBase; 
     return base; 
    } 
} 

class Derived extends Base { 
    private String dataOfDerived; 

    public Derived(Base base) { 
     super(base); 
    } 

    @Override 
    public Object clone() { 
     Base base = super.clone(); 
     Derived derived = new Derived(base); 
     derived.dataOfDerived = dataOfDerived; 
     return derived; 
    } 
} 

Answer 1

你可以在拷貝構造函數方面實現clone：

class Base { 
    private String dataOfBase; 
    ... 
    public Base(Base other) { 
     this.dataOfBase = other.dataOfBase; 
    } 

    @Override 
    public Base clone() { // Covariant return type 
     return new Base(this); // calling copy constructor 
    } 
} 

class Derived extends Base { 
    private String dataOfDerived; 
    ... 
    public Derived(Derived other) { 
     super(other); 
     this.dataOfDerived = other.dataOfDerived; 
    } 

    @Override 
    public Derived clone() { 
     return new Derived(this); 
    } 
} 

Answer 2

出什麼這樣的事情。它將允許您直接克隆層次結構中的任何類，幷包含來自層次結構中更高級的所有類的數據。

public class Derived1 extends Base { 

    public Derived1 clone(Derived1 foo) { 
     super.clone(foo); 
     // copy fields from Derived1 
     return foo; 
    } 

    public Derived1 clone() { 
     Derived1 foo = new Derived1(); 
     return this.clone(foo); 
    } 

}