浅拷贝与深拷贝

浅拷贝和深拷贝的错误容易出现在引用类型中，当一个引用类型含有引用类型的成员变量，比如下方的源代码中引用类型Employee含有引用类型的成员变量name，当有类似情形时，会比较容易造成浅拷贝与深拷贝的混淆。

package copy;public class Employee implements Cloneable{    private String name = "";    private int age = 0;    public Employee(String name, int age) {        super();        this.name = name;        this.age = age;    }    @Override    public Employee clone() throws CloneNotSupportedException {        Employee copy = (Employee) super.clone();        String name = new String(this.name);        copy.setName(name);        return copy;    }    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 static void main(String[] args) {        Employee employee = new Employee("Original employee", 10);        Employee copy = null;        try {            copy = employee.clone();        } catch (CloneNotSupportedException e) {            e.printStackTrace();        }        System.out.println("employee == copy? " + (employee == copy));        System.out.println("employee'name == copy'name? " + (employee.getName() == copy.getName()));    }}

当我们只这样重写clone方法时，那Employee调用clone时将会是浅拷贝，从输出也能看的出来

@Override    public Employee clone() throws CloneNotSupportedException {        Employee copy = (Employee) super.clone();        return copy;    }

输出

employee == copy? falseemployee'name == copy'name? true

所以这种情况是需要特别注意的地方。

如果我们需要深拷贝（Deep Copy），那需要对Employee内的所有引用类型再进行重新new，这样就可以进行深度拷贝。

@Overridepublic Employee clone() throws CloneNotSupportedException {    Employee copy = (Employee) super.clone();    String name = new String(this.name);    copy.setName(name);    return copy;}

employee == copy? falseemployee'name == copy'name? false