详解java中的深拷贝和浅拷贝（clone()方法的重写、使用序列化实现真正的深拷贝）

public class CloneUtils {  @SuppressWarnings("unchecked")  public static <T extends Serializable> T clone(T object){    T cloneObj = null;    try {      ByteArrayOutputStream out = new ByteArrayOutputStream();      ObjectOutputStream obs = new ObjectOutputStream(out);      obs.writeObject(object);      obs.close();      ByteArrayInputStream ios = new ByteArrayInputStream(out.toByteArray());      ObjectInputStream ois = new ObjectInputStream(ios);      cloneObj = (T) ois.readObject();    }catch (Exception e){      e.printStackTrace();    }    return cloneObj;  }}

public class TestString {  public static void main(String[] args) {    TestString test = new TestString();    System.out.println("-------浅拷贝---------");    test.qianCopyTest();    System.out.println();    System.out.println("--------使用clone深拷贝--------");    test.defaultCloneTest();    System.out.println();    System.out.println("--------使用序列化实现对象的拷贝--------");    test.streamClonrTest();    System.out.println("--------耗时对比--------");    System.out.println("耗时1 : "+ test.qianCopyCost());    System.out.println("耗时2 : "+ test.CloneCopyCost());    System.out.println("耗时3 : "+ test.StreamCopyCost());  }  /*浅拷贝*/  private void qianCopyTest() {    String s = "cd";    change(s);    System.out.println(s);    System.out.println("----------------");    String b = new String("cd");    change(b);    System.out.println(b);    System.out.println("----------------");    int me = 1;    change(me);    System.out.println(me);    System.out.println("----------------");    Person person = new Person("我", 13,new Email("我"));    change(person);    System.out.println(person.toString());  }  /*使用默认的clone方法，需要Person实现Cloneable接口*/  private void defaultCloneTest(){    Person person = new Person("我", 13,new Email("我"));    Person person1 = person.clone();    Person person2 = person.clone();    System.out.println("person : 【"+person+"】");    System.out.println("person1 : 【"+person1+"】");    System.out.println("person2 : 【"+person2+"】");    //改一个就会触动全部！！ 这就是使用默认的clone方法的弊端    /*该clone()方法是使用Object类的clone()方法，但是该方法存在一个缺陷，它并不会将对象的所有属性全部拷贝过来，而是有选择性的拷贝，基本规则如下：       1、 基本类型         如果变量是基本很类型，则拷贝其值，比如int、float等。       2、 对象         如果变量是一个实例对象，则拷贝其地址引用，也就是说此时新对象与原来对象是公用该实例变量。       3、 String字符串         若变量为String字符串，则拷贝其地址引用。但是在修改时，它会从字符串池中重新生成一个新的字符串，原有紫都城对象保持不变。*/    person.getEmail().setContent("你");    System.out.println("之后的person : 【"+person+"】");    System.out.println("之后的person1 : 【"+person1+"】");    System.out.println("之后的person2 : 【"+person2+"】");  }  /*使用序列化实现对象的拷贝，需要对象以及对象中的其他对象都要实现Serializable接口*/  private void streamClonrTest(){    Person person = new Person("我", 13,new Email("我"));    Person person1 = CloneUtils.clone(person);    Person person2 = CloneUtils.clone(person);    System.out.println("person : 【"+person+"】");    System.out.println("person1 : 【"+person1+"】");    System.out.println("person2 : 【"+person2+"】");    person.getEmail().setContent("你");    System.out.println("之后的person : 【"+person+"】");    System.out.println("之后的person1 : 【"+person1+"】");    System.out.println("之后的person2 : 【"+person2+"】");  }  private static void change(String x) {    x = "ab";  }  private static void change(int x) {    x = 2;  }  private static void change(Person x) {    x = new Person("你", 20, new Email("你"));  }  private long qianCopyCost(){    long start = System.currentTimeMillis();    Person person = new Person("我", 13,new Email("我"));    List<Person> list = new ArrayList<>();    for(int i = 0;i<=10000;i++){      list.add(new Person("你", 20, new Email("你")));    }    return System.currentTimeMillis()-start;  }  private long CloneCopyCost(){    long start = System.currentTimeMillis();    Person person = new Person("我", 13,new Email("我"));    List<Person> list = new ArrayList<>();    for(int i = 0;i<=10000;i++){      list.add(person.clone());    }    return System.currentTimeMillis()-start;  }  private long StreamCopyCost(){    long start = System.currentTimeMillis();    Person person = new Person("我", 13,new Email("我"));    List<Person> list = new ArrayList<>();    for(int i = 0;i<=10000;i++){      list.add(CloneUtils.clone(person));    }    return System.currentTimeMillis()-start;  }}class Person implements Serializable, Cloneable {  private static final long serialVersionUID = -8584225043397465132L;  private String name;  private int age;  public void setEmail(Email email) {    this.email = email;  }  private Email email;  public Email getEmail() {    return email;  }  public void setName(String name) {    this.name = name;  }  public void setAge(int age) {    this.age = age;  }  public Person(String name, int age, Email email) {    this.name = name;    this.age = age;    this.email = email;  }  @Override  public String toString() {    return "name : " + name + " | age : " + age +" | content : "+email.getContent();  }  @Override  protected Person clone() {    Person person = null;    try {      person = (Person) super.clone();      /*如果加上下一行 “使用clone深拷贝” 就不会改一处其他都改变了*/      person.setEmail(new Email(person.getEmail().getContent()));    } catch (CloneNotSupportedException e) {      e.printStackTrace();    }    return person;  }}class Email implements Serializable {  private static final long serialVersionUID = 1426052929769365539L;  private String content;  public void setContent(String content) {    this.content = content;  }  public String getContent() {    return content;  }  public Email(String content) {    this.content = content;  }}