Cloneable接口

Cloneable接口：实现此接口，以指示Object.clone()可以合法的对该类实例进行按字段复制。如果没有实现Object的clone方法，则会导致抛出CloneNotSupportedException异常。复制分2种：

1. 浅表复制：被克隆对象内部成员变量只含基本数据类型时，只需进行浅表复制
2. 深表复制：被克隆对象内部成员变量含有非基本数据类型时，需要进行深表复制

浅表复制：

class Student implements Cloneable {
    public String name;
    public int age;

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

    // 浅表复制，被克隆对象内所有成员变量都为基本类型时
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            throw new Error(e.getMessage());
        }
    }

}

 

 深表复制：

class Teacher implements Cloneable {
    public String name;
    public Student student1;
    public Student student2;

    public Teacher(String name, Student student1, Student student2)   {
        this.name = name;
        this.student1 = student1;
        this.student2 = student2;
    }

    // 深表复制，被克隆对象内含有非基本类型成员变量时
    public Object clone() {
        try {
            Teacher t = (Teacher) super.clone();
            t.student1 = (Student) student1.clone();    //深表复制
            //t.student2 = (Student) student2.clone();
            //this.student2将不会被复制，t.student2只保存this.student2实例的引用
            return t;
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
            throw new Error(e.getMessage());
        }
    }
}

 

测试：

 

public class CloneableTest {
    public static void main(String[] args) {
        Student s1 = new Student("s1", 13);
        Student s2 = new Student("s2", 14);
        Teacher t = new Teacher("t", s1, s2);
        Teacher t2 = (Teacher) t.clone();
        Student s3 = (Student) s1.clone();
        
        System.out.println(s3.name);    //输出：s1
        s1.name = "ss1";
        System.out.println(s3.name);    //输出：s1，    
        //浅表复制成功，说明基本类型成员变量只需浅表复制即可
        
        System.out.println(t2.student1.name);   //输出：s1
        System.out.println(t2.student2.name);   //输出：s2
        t.student1.name = "s11";
        t.student2.name = "s22";
        System.out.println(t2.student1.name);   //输出：s1
        System.out.println(t2.student2.name);   //输出：ss2
        //在Teacher类的clone方法中，student2没有进行深表复制，克隆出来的t1.student2
        //只保存了t.student2实例的引用，当t.student2改变时t1.student2将跟着改变
    }
}