Java中的淺拷貝與深拷貝 + Serializable的傳送鏈接

Java中的等號賦值

Java的內存處理分爲堆和棧，將基本變量（int , long, String變量值）存儲在棧中，將對象指向堆的地址放在棧中，這就是說，如果對基本類型做等號賦值，就直接在棧中開闢內存空間存儲，但對對象卻只是重新開闢空間存儲之前對象的地址。
如下代碼給出說明

class Test
{
    public static void main(String arg[])
    {
        String s = "Brother Xiang";
        String t = s;
        t = t + " is very handsome!";
        System.out.println(s);//輸出爲Brother Xiang
        System.out.println(t);//輸出爲Brother Xiang is very handsome!
    }
}

說明將s， t 對應不同的String對象，修改t時不會影響s的值，以下爲對對象的賦值

class Student
{
    private String name;
    private int age;

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

    public void setName(String name)
    {
        this.name = name;
    }

    public String toString()
    {
        StringBuilder s = new StringBuilder();
        s.append("Name: " + name + "  " + "Age: " + age);
        return s.toString();
    }
}

class Test
{
    public static void main(String arg[])
    {
        Student student1 = new Student("Bob", 14);
        Student student2 = student1;
        student2.setName("Jhon");

        System.out.print("student1: ");
        System.out.println(student1);
        System.out.print("student2: ");
        System.out.println(student2);
    }
}

執行結果爲

可以看出，修改student2同時也修改了student1，這說明只賦值了對對象的引用

Java中淺拷貝與深拷貝

Java當中淺拷貝和深拷貝都是對於對象級別的來說的，淺拷貝和深拷貝的不同由如下代碼就能看出

淺拷貝與深拷貝的簡單形式

//淺拷貝只在Student類上加上Cloneable接口
//深拷貝則需要在Address類與Student類加上Cloneable接口

class Address
{
    private String province;
    private String city;
    public Address(String province, String city)
    {
        this.province = province;
        this.city = city;
    }
    public void setProvince(String province)
    {
        this.province = province;
    }
    public void setCity(String city)
    {
        this.city = city;
    }
    public String toString()
    {
        StringBuilder s = new StringBuilder();
        s.append("Location at: " + province + " " + city);
        return s.toString();
    }
}

class Student  implements Cloneable
{
    private String name;
    private int age;
    private Address address;

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

    public void setName(String name)
    {
        this.name = name;
    }

    public Address getAddress()
    {
        return address;
    }

    public String toString()
    {
        StringBuilder s = new StringBuilder();
        s.append("Name: " + name + "  " + "Age: " + age + "  "+ address);
        return s.toString();
    }

    public Student clone()
    {
        Student temp = null;
        try
        {
            temp = (Student)super.clone();  
        }
        catch(CloneNotSupportedException e)
        {
            e.printStackTrace();
        }
        return temp;
    }
}

class Test
{
    public static void main(String arg[])
    {
        Address address = new Address("GuangDong", "GuangZhou");
        Student student1 = new Student("Bob", 14, address);
        Student student2 = student1.clone();

        student2.setName("Jhon");
        Address student2_address = student2.getAddress();
        student2_address.setProvince("GuiZhou");
        student2_address.setCity("GuiYang");

        System.out.print("student1: ");
        System.out.println(student1);
        System.out.print("student2: ");
        System.out.println(student2);
    }
}
//它們兩個具體區別在於，淺拷貝通過address訪問Address類中方法時，student2的address發生改變，student1也發生改變，而深拷貝卻不會發生改變，本代碼僅給出淺拷貝的實現方式。

輸出結果如下：

對對象的名字和地址進行改變時，其值也相應發生了改變，

淺拷貝與深拷貝的Serializable形式

傳送門（轉載鏈接）：快樂燕子會飛——java serializable深入瞭解