Java 8提供了一种优雅而简洁地调用元素狗的复制构造函数或克隆方法的新方法:流、lambdas和收集器。

拷贝构造函数:

List<Dog> clonedDogs = dogs.stream().map(Dog::new).collect(toList());

表达式Dog::new被称为方法引用。它创建了一个函数对象，调用Dog上的构造函数，该构造函数以另一个Dog作为参数。

克隆方法[1]:

List<Dog> clonedDogs = dogs.stream().map(Dog::clone).collect(toList());

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得到一个数组列表作为结果

或者，如果你必须得到一个数组列表(以防你以后想修改它):

ArrayList<Dog> clonedDogs = dogs.stream().map(Dog::new).collect(toCollection(ArrayList::new));

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及时更新列表

如果你不需要保留狗列表的原始内容，你可以使用replaceAll方法并在适当的地方更新列表:

dogs.replaceAll(Dog::new);

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所有示例都假设导入静态java.util.stream.Collectors.*;

---

数组列表收集器

上一个例子中的收集器可以被做成一个util方法。因为这是一件很常见的事情，我个人喜欢它是短而漂亮的。是这样的:

ArrayList<Dog> clonedDogs = dogs.stream().map(d -> d.clone()).collect(toArrayList());

public static <T> Collector<T, ?, ArrayList<T>> toArrayList() {
    return Collectors.toCollection(ArrayList::new);
}

---

[1] CloneNotSupportedException异常说明:

为了使这个解决方案工作，Dog的克隆方法不能声明它抛出CloneNotSupportedException。原因是map的参数不允许抛出任何受控异常。

是这样的:

    // Note: Method is public and returns Dog, not Object
    @Override
    public Dog clone() /* Note: No throws clause here */ { ...

然而，这应该不是一个大问题，因为这是最佳实践。(例如，effective Java给出了这个建议。)

感谢Gustavo注意到这一点。

简单的方法，使用common -lang-2.3.jar的java库克隆列表

链接下载commons-lang-2.3.jar

如何使用

oldList.........
List<YourObject> newList = new ArrayList<YourObject>();
foreach(YourObject obj : oldList){
   newList.add((YourObject)SerializationUtils.clone(obj));
}

我希望这篇文章能有所帮助。

:D

我想我找到了一个非常简单的方法来创建一个深度复制数组列表。假设你想复制一个字符串数组列表arrayA。

ArrayList<String>arrayB = new ArrayList<String>();
arrayB.addAll(arrayA);

如果对你不起作用请告诉我。

一些其他用于将ArrayList复制为深度复制的替代方法

Alernative 1 -使用外部包common -lang3，方法SerializationUtils.clone():

SerializationUtils.clone()

假设我们有一个类dog，其中类的字段是可变的，并且至少有一个字段是String类型和mutable类型的对象——而不是基本数据类型(否则浅拷贝就足够了)。

浅拷贝的例子:

List<Dog> dogs = getDogs(); // We assume it returns a list of Dogs
List<Dog> clonedDogs = new ArrayList<>(dogs);

现在回到狗的深度复制。

Dog类只有可变字段。

狗类:

public class Dog implements Serializable {
    private String name;
    private int age;

    public Dog() {
        // Class with only mutable fields!
        this.name = "NO_NAME";
        this.age = -1;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

注意，类Dog实现了Serializable!这使得可以使用方法“SerializationUtils.clone(dog)”

阅读main方法中的注释以理解结果。这表明我们已经成功地对ArrayList()进行了深度复制。看到 在“SerializationUtils.clone(dog)”下面:

public static void main(String[] args) {
    Dog dog1 = new Dog();
    dog1.setName("Buddy");
    dog1.setAge(1);

    Dog dog2 = new Dog();
    dog2.setName("Milo");
    dog2.setAge(2);

    List<Dog> dogs = new ArrayList<>(Arrays.asList(dog1,dog2));

    // Output: 'List dogs: [Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]'
    System.out.println("List dogs: " + dogs);

    // Let's clone and make a deep copy of the dogs' ArrayList with external package commons-lang3:
    List<Dog> clonedDogs = dogs.stream().map(dog -> SerializationUtils.clone(dog)).collect(Collectors.toList());
    // Output: 'Now list dogs are deep copied into list clonedDogs.'
    System.out.println("Now list dogs are deep copied into list clonedDogs.");

    // A change on dog1 or dog2 can not impact a deep copy.
    // Let's make a change on dog1 and dog2, and test this
    // statement.
    dog1.setName("Bella");
    dog1.setAge(3);
    dog2.setName("Molly");
    dog2.setAge(4);

    // The change is made on list dogs!
    // Output: 'List dogs after change: [Dog{name='Bella', age=3}, Dog{name='Molly', age=4}]'
    System.out.println("List dogs after change: " + dogs);

    // There is no impact on list clonedDogs's inner objects after the deep copy.
    // The deep copy of list clonedDogs was successful!
    // If clonedDogs would be a shallow copy we would see the change on the field
    // "private String name", the change made in list dogs, when setting the names
    // Bella and Molly.
    // Output clonedDogs:
    // 'After change in list dogs, no impact/change in list clonedDogs:\n'
    // '[Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]\n'
    System.out.println("After change in list dogs, no impact/change in list clonedDogs: \n" + clonedDogs);
}

输出:

List dogs: [Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]
Now list dogs are deep copied into list clonedDogs.
List dogs after change: [Dog{name='Bella', age=3}, Dog{name='Molly', age=4}]
After change in list dogs, no impact/change in list clonedDogs:
[Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]

备注: 因为改变列表狗后对列表克隆狗没有影响/改变， 那么ArrayList的深度复制成功!

Alernative 2 -不使用外部包:

Dog类中引入了一个新方法“clone()”，与替代方案1相比，“implements Serializable”被删除了。

clone()

狗类:

public class Dog {
    private String name;
    private int age;

    public Dog() {
        // Class with only mutable fields!
        this.name = "NO_NAME";
        this.age = -1;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    /**
     * Returns a deep copy of the Dog
     * @return new instance of {@link Dog}
     */
    public Dog clone() {
        Dog newDog = new Dog();
        newDog.setName(this.name);
        newDog.setAge(this.age);
        return newDog;
    }

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

阅读下面主要方法中的评论以理解结果。这表明我们已经成功地对ArrayList()进行了深度复制。看到 下面是上下文中的“clone()”方法:

public static void main(String[] args) {
    Dog dog1 = new Dog();
    dog1.setName("Buddy");
    dog1.setAge(1);

    Dog dog2 = new Dog();
    dog2.setName("Milo");
    dog2.setAge(2);

    List<Dog> dogs = new ArrayList<>(Arrays.asList(dog1,dog2));

    // Output: 'List dogs: [Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]'
    System.out.println("List dogs: " + dogs);

    // Let's clone and make a deep copy of the dogs' ArrayList:
    List<Dog> clonedDogs = dogs.stream().map(dog -> dog.clone()).collect(Collectors.toList());
    // Output: 'Now list dogs are deep copied into list clonedDogs.'
    System.out.println("Now list dogs are deep copied into list clonedDogs.");

    // A change on dog1 or dog2 can not impact a deep copy.
    // Let's make a change on dog1 and dog2, and test this
    // statement.
    dog1.setName("Bella");
    dog1.setAge(3);
    dog2.setName("Molly");
    dog2.setAge(4);

    // The change is made on list dogs!
    // Output: 'List dogs after change: [Dog{name='Bella', age=3}, Dog{name='Molly', age=4}]'
    System.out.println("List dogs after change: " + dogs);

    // There is no impact on list clonedDogs's inner objects after the deep copy.
    // The deep copy of list clonedDogs was successful!
    // If clonedDogs would be a shallow copy we would see the change on the field
    // "private String name", the change made in list dogs, when setting the names
    // Bella and Molly.
    // Output clonedDogs:
    // 'After change in list dogs, no impact/change in list clonedDogs:\n'
    // '[Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]\n'
    System.out.println("After change in list dogs, no impact/change in list clonedDogs: \n" + clonedDogs);
}

输出:

List dogs: [Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]
Now list dogs are deep copied into list clonedDogs.
List dogs after change: [Dog{name='Bella', age=3}, Dog{name='Molly', age=4}]
After change in list dogs, no impact/change in list clonedDogs:
[Dog{name='Buddy', age=1}, Dog{name='Milo', age=2}]

备注: 因为改变列表狗后对列表克隆狗没有影响/改变， 那么ArrayList的深度复制成功!

注一: 方案1比方案2慢得多， 但更容易维护，因为您不需要 更新任何方法，如clone()。

注2:对于替代方案1，以下maven依赖项用于方法“SerializationUtils.clone()””:

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-lang3 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.9</version>
</dependency>

更多common-lang3版本请访问:

https://mvnrepository.com/artifact/org.apache.commons/commons-lang3

我刚刚开发了一个库，能够克隆一个实体对象和java.util.List对象。只需从https://drive.google.com/open?id=0B69Sui5ah93EUTloSktFUkctN0U下载jar，并使用静态方法cloneListObject(List List)。该方法不仅克隆List，而且克隆所有实体元素。

您可以使用JSON(带有JSON库)来序列化和反序列化列表。序列化后的列表在未序列化时不包含对原始对象的引用。

使用谷歌GSON:

List<CategoryModel> originalList = new ArrayList<>(); // add some items later
String listAsJson = gson.toJson(originalList);
List<CategoryModel> newList = new Gson().fromJson(listAsJson, new TypeToken<List<CategoryModel>>() {}.getType());

你也可以使用其他JSON库，比如Jackson。

使用这种方法的优点是可以解决问题，而不必创建类、接口和克隆逻辑(如果对象内部有其他对象列表，克隆逻辑可能会很长)