前言

由于最近写业务逻辑的时候遇到了浅拷贝与深拷贝问题，因此特地记录一下。

定义一个实体类Person

public class Person implements Cloneable{
    private String name;
    private int age;

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

    @Override
    public Object clone()  {
        Person person = null;
        try {
            person = (Person) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return person;
    }

    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;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

深拷贝

public class TeamA implements Cloneable {
    private int classNo;
    private List<Person> persons;

    public TeamA(int classNo, List<Person> persons) {
        this.classNo = classNo;
        this.persons = persons;
    }

    @Override
    public Object clone() {
        TeamA team = null;
        try {
            team = (TeamA) super.clone();
            List<Person> personList = new ArrayList<>();
            for (int i = 0; i < persons.size(); i++) {
                personList.add((Person) persons.get(i).clone());
            }
            team.persons = personList;
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return team;
    }

    public int getClassNo() {
        return classNo;
    }

    public void setClassNo(int classNo) {
        this.classNo = classNo;
    }

    public List<Person> getPersons() {
        return persons;
    }

    public void setPersons(List<Person> persons) {
        this.persons = persons;
    }

    @Override
    public String toString() {
        return "Team{" +
                "classNo=" + classNo +
                ", persons=" + persons +
                '}';
    }
}

测试代码

    public static void testA() {
        List<Person> personList = new ArrayList<>();
        personList.add(new Person("Jeremy",18));

        TeamA teamA1 = new TeamA(1, personList);
        TeamA teamA2 = (TeamA) teamA1.clone();

        Log.d("deepCopy","before teamA1 = " + teamA1);
        Log.d("deepCopy","before teamA2 = " + teamA2);

        teamA1.getPersons().add(new Person("Sun", 36));
        teamA1.setClassNo(2);

        Log.d("deepCopy","after teamA1 = " + teamA1);
        Log.d("deepCopy","after teamA2 = " + teamA2);
    }

测试结果

06-11 15:42:23.426 D/deepCopy(11318): before teamA1 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}]}
06-11 15:42:23.426 D/deepCopy(11318): before teamA2 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}]}
06-11 15:42:23.426 D/deepCopy(11318): after teamA1 = Team{classNo=2, persons=[Student{name='Jeremy', age=18}, Student{name='Sun', age=36}]}
06-11 15:42:23.426 D/deepCopy(11318): after teamA2 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}]}

浅拷贝

public class TeamB implements Cloneable {
    private int classNo;
    private List<Person> persons;

    public TeamB(int classNo, List<Person> persons) {
        this.classNo = classNo;
        this.persons = persons;
    }

    @Override
    public Object clone() {
        TeamB team = null;
        try {
            team = (TeamB) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return team;
    }

    public int getClassNo() {
        return classNo;
    }

    public void setClassNo(int classNo) {
        this.classNo = classNo;
    }

    public List<Person> getPersons() {
        return persons;
    }

    public void setPersons(List<Person> persons) {
        this.persons = persons;
    }

    @Override
    public String toString() {
        return "Team{" +
                "classNo=" + classNo +
                ", persons=" + persons +
                '}';
    }
}

测试代码

public static void testB() {
        List<Person> personList = new ArrayList<>();
        personList.add(new Person("Jeremy",18));

        TeamB teamB1 = new TeamB(1, personList);
        TeamB teamB2 = (TeamB) teamB1.clone();

        Log.d("shallowCopy","before teamB1 = " + teamB1);
        Log.d("shallowCopy","before teamB2 = " + teamB2);

        teamB1.getPersons().add(new Person("Sun", 36));
        teamB1.setClassNo(2);

        Log.d("shallowCopy","after teamB1 = " + teamB1);
        Log.d("shallowCopy","after teamB2 = " + teamB2);
    }

测试结果

06-11 15:42:23.428 D/shallowCopy(11318): before teamB1 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}]}
06-11 15:42:23.428 D/shallowCopy(11318): before teamB2 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}]}
06-11 15:42:23.431 D/shallowCopy(11318): after teamB1 = Team{classNo=2, persons=[Student{name='Jeremy', age=18}, Student{name='Sun', age=36}]}
06-11 15:42:23.431 D/shallowCopy(11318): after teamB2 = Team{classNo=1, persons=[Student{name='Jeremy', age=18}, Student{name='Sun', age=36}]}