Java中的浅拷贝与深拷贝

Java中的浅拷贝与深拷贝

1.浅拷贝含义：
对于基本类型来讲都是值的引用，但是对于引用类型来讲，拷贝的是同一个引用，也就是同一个首地址的对象，它所指的堆内存都是一样的。
2.深拷贝含义：
对于基本类型来讲都是值的引用，但是对于引用类型来讲，会再创建一个新的对象，指向另一个首地址。

班级类拷贝方法为浅拷贝
public class Classes implements Cloneable{
/*

• 学生
  */
  private Student student;

  /
  班级名称
  */
  private String classesName;

  /班级编号
  /
  private String classesCode;

  public Classes(Student student, String classesName, String classesCode) {
  super();
  this.student = student;
  this.classesName = classesName;
  this.classesCode = classesCode;
  }

  public Student getStudent() {
  return student;
  }

  public void setStudent(Student student) {
  this.student = student;
  }

  public String getClassesName() {
  return classesName;
  }

  public void setClassesName(String classesName) {
  this.classesName = classesName;
  }

  public String getClassesCode() {
  return classesCode;
  }

  public void setClassesCode(String classesCode) {
  this.classesCode = classesCode;
  }

  public Object clone() throws CloneNotSupportedException {
  return super.clone();
  }
  }

/**

• 学生类
• @author win 10

• /
  public class Student implements Cloneable{
  /

  • 姓名
    */
    private String name;

  /*

  • 年龄
    */
    private int age;

  public Student(String name, int age) {
  super();
  this.name = name;
  this.age = age;
  }

  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;
  }

}

测试类：
public class TestClone {
public static void main(String[] args) {
Student stu = new Student("张三",16);
Classes cla = new Classes(stu,"初一(2)班","002");
System.out.println("原对象:"+cla);
System.out.println("原对象student属性"+stu);
System.out.println("姓名:"+cla.getStudent().getName()+"年龄:"+cla.getStudent().getAge());
try {
Classes cla2 = (Classes)cla.clone();
//重新设置拷贝对象student的年龄属性,用于观察是否会影响到原对象的student年龄属性
cla2.getStudent().setAge(18);
System.out.println("拷贝对象:"+cla2);
System.out.println("拷贝对象student属性:"+cla2.getStudent());
System.out.println("拷贝对象姓名:"+cla2.getStudent().getName()+"年龄:"+cla2.getStudent().getAge());
System.out.println("原对象姓名:"+cla.getStudent().getName()+"年龄:"+cla.getStudent().getAge());
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
}
}
测试结果：

虽然Classes对象已经是深拷贝，但是Classes对象里的Student对象并没有做到深拷贝。拷贝出来的Classes对象的Student属性会跟随着原Classes的Student的变化而变化同样的原Classes的Student也会跟着拷贝后的Student变化后变化。

改版后的代码:
package Clone;

/**

• 班级类
• @author win 10

• /
  public class Classes implements Cloneable{
  /

  • 学生
    */
    private Student student;

  /
  班级名称
  */
  private String classesName;

  /班级编号
  /
  private String classesCode;

  public Classes(Student student, String classesName, String classesCode) {
  super();
  this.student = student;
  this.classesName = classesName;
  this.classesCode = classesCode;
  }

  public Student getStudent() {
  return student;
  }

  public void setStudent(Student student) {
  this.student = student;
  }

  public String getClassesName() {
  return classesName;
  }

  public void setClassesName(String classesName) {
  this.classesName = classesName;
  }

  public String getClassesCode() {
  return classesCode;
  }

  public void setClassesCode(String classesCode) {
  this.classesCode = classesCode;
  }

  public Object clone() throws CloneNotSupportedException {
  Classes cla = (Classes)super.clone();
  cla.student = (Student)student.clone();
  return cla;
  }
  }
  将Stundent引用类型也做一个深拷贝

package Clone;

/**

• 学生类
• @author win 10

• /
  public class Student implements Cloneable{
  /

  • 姓名
    */
    private String name;

  /年龄
  /
  private int age;

  public Student(String name, int age) {
  super();
  this.name = name;
  this.age = age;
  }

  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;
  }
  public Object clone() throws CloneNotSupportedException {
  return super.clone();
  }
  }
  Student也加上拷贝方法
  测试结果：
  

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