Java 拷贝方式

Java 有哪几种拷贝方式，哪种拷贝效率高

数组拷贝

　  @Test
    public void ArrayClone() {
        
        //普通for循环复制数组
        int[] oldArray = {1,2,3,4,5,6,7,8,9,10};
        int[] newArray = new int[oldArray.length];
        for(int i=0; i<oldArray.length; i++) {
            newArray[i]=oldArray[i];
        }
        System.out.println(Arrays.toString(newArray));
        
        //System.arraycopy
        int[] intArray = new int[oldArray.length];
        System.arraycopy(oldArray, 0, intArray, 0, oldArray.length);
        System.out.println(Arrays.toString(intArray));
        
        //Arrays.copyOf 方法实现也是调用 System.arraycopy
        int[] array = new int[oldArray.length];
        array = Arrays.copyOf(oldArray, oldArray.length);
        System.out.println(Arrays.toString(array));
        
        //clone 对于基本数据类型clone是浅拷贝
        int[] nums = new int[oldArray.length];
        nums = oldArray.clone();
        System.out.println(Arrays.toString(nums));
    }

对象拷贝

    @Test
    public void objectClone() throws CloneNotSupportedException, IllegalAccessException, InvocationTargetException {
        Person tom = new Person("Tom", 12);
        
        //引用拷贝
        Person mark = tom;
        System.out.println(mark.getName() + " " + mark.getAge());
        
        //clone
        Person xiaoming = (Person) tom.clone();
        tom.setAge(23);
        System.out.println(xiaoming.getName() + " " + xiaoming.getAge());
        
        //Student类必须是public修饰的
        //BeanUtils.copyProperties
        Student student = new Student("小明", "12345", 24);
        Student lilei = new Student();
        BeanUtils.copyProperties(lilei, student);
        System.out.println(lilei.getName() + "  " + lilei.getNo() + "  " + lilei.getAge());
        
        //Map转对象
        Map<String, Object> map = new HashMap<>();
        map.put("name", "小刚");
        map.put("no", "110");
        map.put("age", 100);
        
        Student xiaogang = new Student();
        BeanUtils.copyProperties(xiaogang, map);
        System.out.println(xiaogang.getName() + "  " + xiaogang.getNo() + "  " + xiaogang.getAge());
    }

public class Person implements Cloneable {
    
    private String name;
    private Integer age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public Person(String name, Integer age) {
        super();
        this.name = name;
        this.age = age;
    }
    public Person() {}
    
    //实现clone方法
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
    
}

import java.io.Serializable;

public class Student implements Serializable {
    private static final long serialVersionUID = 1L;
    private String name;
    private String no;
    private Integer age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getNo() {
        return no;
    }
    public void setNo(String no) {
        this.no = no;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public Student(String name, String no, Integer age) {
        super();
        this.name = name;
        this.no = no;
        this.age = age;
    }
    public Student() {}
    @Override
    public String toString() {
        return "Student [name=" + name + ", no=" + no + ", age=" + age + "]";
    }
    
}

实现Serializable接口实现对象拷贝

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import www.maxinhai.com.Student;

public class Teacher implements Serializable {
    
    private static final long serialVersionUID = 1L;
    private String name;
    private Student student;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Student getStudent() {
        return student;
    }
    public void setStudent(Student student) {
        this.student = student;
    }
    public Object deepCopy() throws ClassNotFoundException, IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream  oos = new ObjectOutputStream(bos);
        oos.writeObject(this);
        //将当前这个对象写到一个输出流当中，，因为这个对象的类实现了Serializable这个接口，所以在这个类中
        //有一个引用，这个引用如果实现了序列化，那么这个也会写到这个输出流当中
        
        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bis);
        return ois.readObject();
        //这个就是将流中的东西读出类，读到一个对象流当中，这样就可以返回这两个对象的东西，实现深克隆
    }
    @Override
    public String toString() {
        return "Teacher [name=" + name + ", student=" + student + "]";
    }
    
}

    @Test
    public void testSerializable() throws ClassNotFoundException, IOException {
        Teacher teacher = new Teacher();
        teacher.setName("李老师");
        Student student = new Student("小明", "12345", 24);
        teacher.setStudent(student);
        
        Teacher teacherLi = new Teacher();
        teacherLi = (Teacher) teacher.deepCopy();
        teacher.setName("teacher Li");
        System.out.println(teacherLi.toString());
    }