Java中的淺拷貝與深拷貝

Java中的淺拷貝與深拷貝

1.淺拷貝含義：
對于基本類型來講都是值的引用，但是對于引用類型來講，拷貝的是同一個引用，也就是同一個首地址的對象，它所指的堆內存都是一樣的。
2.深拷貝含義：
對于基本類型來講都是值的引用，但是對于引用類型來講，會再創建一個新的對象，指向另一個首地址。

班級類拷貝方法為淺拷貝
public class Classes implements Cloneable{
/*

• 學生
  */
  private Student student;

  /
  班級名稱
  */
  private String classesName;

  /班級編號
  /
  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();
  }
  }

/**

• 學生類
• @author win 10

• /
  public class Student implements Cloneable{
  /

  • 姓名
    */
    private String name;

  /*

  • 年齡
    */
    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;
  }

}

測試類：
public class TestClone {
public static void main(String[] args) {
Student stu = new Student("張三",16);
Classes cla = new Classes(stu,"初一(2)班","002");
System.out.println("原對象:"+cla);
System.out.println("原對象student屬性"+stu);
System.out.println("姓名:"+cla.getStudent().getName()+"年齡:"+cla.getStudent().getAge());
try {
Classes cla2 = (Classes)cla.clone();
//重新設置拷貝對象student的年齡屬性,用于觀察是否會影響到原對象的student年齡屬性
cla2.getStudent().setAge(18);
System.out.println("拷貝對象:"+cla2);
System.out.println("拷貝對象student屬性:"+cla2.getStudent());
System.out.println("拷貝對象姓名:"+cla2.getStudent().getName()+"年齡:"+cla2.getStudent().getAge());
System.out.println("原對象姓名:"+cla.getStudent().getName()+"年齡:"+cla.getStudent().getAge());
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
}
}
測試結果：

雖然Classes對象已經是深拷貝，但是Classes對象里的Student對象并沒有做到深拷貝。拷貝出來的Classes對象的Student屬性會跟隨著原Classes的Student的變化而變化同樣的原Classes的Student也會跟著拷貝后的Student變化后變化。

改版后的代碼:
package Clone;

/**

• 班級類
• @author win 10

• /
  public class Classes implements Cloneable{
  /

  • 學生
    */
    private Student student;

  /
  班級名稱
  */
  private String classesName;

  /班級編號
  /
  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;
  }
  }
  將Stundent引用類型也做一個深拷貝

package Clone;

/**

• 學生類
• @author win 10

• /
  public class Student implements Cloneable{
  /

  • 姓名
    */
    private String name;

  /年齡
  /
  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也加上拷貝方法
  測試結果：
  

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