Clone 方法的使用(深度克隆)

转载自：http://www.java2000.net/p1235

 

如下的程序，我们克隆羊圈，每个羊圈里有一只羊

package test.lang;

public class Sheep implements Cloneable {
  private String name;

  public String getName() {
    return name;
  }

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

  @Override
  public Sheep clone() throws CloneNotSupportedException {
    return (Sheep) super.clone();
  }

  public static void main(String[] args) throws CloneNotSupportedException {
    Sheepfold sheepfold1 = new Sheepfold();
    sheepfold1.setName("第一个羊圈");
    Sheep sheep1 = new Sheep();
    sheep1.setName("第一只羊");
    sheepfold1.setSheep(sheep1);
    Sheepfold sheepfold2 = sheepfold1.clone();
    sheepfold2.setName("第一个羊圈的克隆");
    System.out.println("sheepfold1.name=" + sheepfold1.getName() + ",sheep.name=" + sheepfold1.getSheep().getName());
    System.out.println("sheepfold2.name=" + sheepfold2.getName() + ",sheep.name=" + sheepfold2.getSheep().getName());
    System.out.println("sheepfold1.sheep==sheepfold1.sheep?" + (sheepfold1.getSheep() == sheepfold2.getSheep()));
  }
}

class Sheepfold implements Cloneable {
  private String name;

  private Sheep sheep;

  @Override
  public Sheepfold clone() throws CloneNotSupportedException {
    Sheepfold o = (Sheepfold) super.clone();

    return o;
  }

  public String getName() {
    return name;
  }

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

  public Sheep getSheep() {
    return sheep;
  }

  public void setSheep(Sheep sheep) {
    this.sheep = sheep;
  }
}

package test.lang;

public class Sheep implements Cloneable {
  private String name;

  public String getName() {
    return name;
  }

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

  @Override
  public Sheep clone() throws CloneNotSupportedException {
    return (Sheep) super.clone();
  }

  public static void main(String[] args) throws CloneNotSupportedException {
    Sheepfold sheepfold1 = new Sheepfold();
    sheepfold1.setName("第一个羊圈");
    Sheep sheep1 = new Sheep();
    sheep1.setName("第一只羊");
    sheepfold1.setSheep(sheep1);
    Sheepfold sheepfold2 = sheepfold1.clone();
    sheepfold2.setName("第一个羊圈的克隆");
    System.out.println("sheepfold1.name=" + sheepfold1.getName() + ",sheep.name=" + sheepfold1.getSheep().getName());
    System.out.println("sheepfold2.name=" + sheepfold2.getName() + ",sheep.name=" + sheepfold2.getSheep().getName());
    System.out.println("sheepfold1.sheep==sheepfold1.sheep?" + (sheepfold1.getSheep() == sheepfold2.getSheep()));
  }
}

class Sheepfold implements Cloneable {
  private String name;

  private Sheep sheep;

  @Override
  public Sheepfold clone() throws CloneNotSupportedException {
    Sheepfold o = (Sheepfold) super.clone();

    return o;
  }

  public String getName() {
    return name;
  }

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

  public Sheep getSheep() {
    return sheep;
  }

  public void setSheep(Sheep sheep) {
    this.sheep = sheep;
  }
}

运行结果如下：

sheepfold1.name=第一个羊圈,sheep.name=第一只羊
sheepfold2.name=第一个羊圈的克隆,sheep.name=第一只羊
sheepfold1.sheep==sheepfold1.sheep?true

sheepfold1.name=第一个羊圈,sheep.name=第一只羊
sheepfold2.name=第一个羊圈的克隆,sheep.name=第一只羊
sheepfold1.sheep==sheepfold1.sheep?true

克隆的羊圈，里面的羊还是第一个羊圈的羊，他们完全相同.并没有被克隆过来，这就是浅层克隆，我们调整代码，实现深层克隆

@Override
public Sheepfold clone() throws CloneNotSupportedException {
  Sheepfold o = (Sheepfold) super.clone();
  o.sheep = this.sheep.clone();
  return o;
}

  @Override
  public Sheepfold clone() throws CloneNotSupportedException {
    Sheepfold o = (Sheepfold) super.clone();
    o.sheep = this.sheep.clone();
    return o;
  }

运行结果

sheepfold1.name=第一个羊圈,sheep.name=第一只羊
sheepfold2.name=第一个羊圈的克隆,sheep.name=第一只羊
sheepfold1.sheep==sheepfold1.sheep?false