Shulou(Shulou.com)06/03 Report--

Shallow copy and Deep copy in Java

1. Shallow copy meaning:

For the basic type, it is a reference to the value, but for the reference type, it copies the same reference, that is, an object with the same first address, which refers to the same heap memory.

two。 Meaning of deep copy:

For the basic type, it is a reference to the value, but for the reference type, a new object is created pointing to another first address.

The copy method of class class is shallow copy.

Public class Classes implements Cloneable {

/ *

Students

, /

Private Student student

/

Class name

, /

Private String classesName

/ Class number

/

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 ()

}

}

/ * *

Student @ author win 10

/

Public class Student implements Cloneable {

/

Name

, /

Private String name

/ *

Age

, /

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

}

}

Test class:

Public class TestClone {

Public static void main (String [] args) {

Student stu = new Student (Zhang San, 16)

Classes cla = new Classes (stu, Class 2, Grade 8)

System.out.println ("original object:" + cla)

System.out.println ("original object student attribute" + stu)

System.out.println ("name:" + cla.getStudent (). GetName () + "Age:" + cla.getStudent (). GetAge ())

Try {

Classes cla2 = (Classes) cla.clone ()

/ / reset the age attribute of the copy object student to observe whether it will affect the student age attribute of the original object.

Cla2.getStudent (). SetAge (18)

System.out.println ("copy object:" + cla2)

System.out.println ("copy object student attribute:" + cla2.getStudent ())

System.out.println ("copy object name:" + cla2.getStudent () .getName () + "Age:" + cla2.getStudent () .getAge ())

System.out.println ("original object name:" + cla.getStudent () .getName () + "Age:" + cla.getStudent () .getAge ())

} catch (CloneNotSupportedException e) {

E.printStackTrace ()

}

}

}

Test results:

Although the Classes object has been deeply copied, the Student object in the Classes object has not been deeply copied. The Student attribute of the copied Classes object will change with the change of the Student of the original Classes, and the Student of the original Classes will also change with the copied Student.

Revised code:

Package Clone

/ * *

Class @ author win 10

/

Public class Classes implements Cloneable {

/

Students

, /

Private Student student

/

Class name

, /

Private String classesName

/ Class number

/

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

}

}

Also make a deep copy of the Stundent reference type

Package Clone

/ * *

Student @ author win 10

/

Public class Student implements Cloneable {

/

Name

, /

Private String name

/ Age

/

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 also adds copy method.

Test results:

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