Java Cloneable用法及代碼示例

// Java program to Demonstrate the 
// application of Cloneable interface 
  
import java.io.*; 
import java.util.*; 
  
class Student { 
  
    // attributes of Student class 
    String name = null; 
    int id = 0; 
  
    // default constructor 
    Student() {} 
  
    // parameterized constructor 
    Student(String name, int id) 
    { 
        this.name = name; 
        this.id = id; 
    } 
    
    public static void main(String[] args) 
    { 
        // create an instance of Student 
        Student s1 = new Student("Ashish", 121); 
  
        // Try to clone s1 and assign 
        // the new object to s2 
        Student s2 = s1.clone(); 
    } 
}

// Java program to illustrate Cloneable interface 
import java.lang.Cloneable; 
  
// By implementing Cloneable interface 
// we make sure that instances of class A 
// can be cloned. 
class A implements Cloneable { 
    int i; 
    String s; 
  
    // A class constructor 
    public A(int i, String s) 
    { 
        this.i = i; 
        this.s = s; 
    } 
  
    // Overriding clone() method 
    // by simply calling Object class 
    // clone() method. 
    @Override
    protected Object clone() 
        throws CloneNotSupportedException 
    { 
        return super.clone(); 
    } 
} 
  
public class Test { 
    public static void main(String[] args) 
        throws CloneNotSupportedException 
    { 
        A a = new A(20, "GeeksForGeeks"); 
  
        // cloning 'a' and holding 
        // new cloned object reference in b 
  
        // down-casting as clone() return type is Object 
        A b = (A)a.clone(); 
  
        System.out.println(b.i); 
        System.out.println(b.s); 
    } 
}

// A Java program to demonstrate deep copy 
// using clone() 
import java.util.ArrayList; 
  
// An object reference of this class is 
// contained by Test2 
class Test { 
    int x, y; 
} 
  
// Contains a reference of Test and implements 
// clone with deep copy. 
class Test2 implements Cloneable { 
    int a, b; 
  
    Test c = new Test(); 
  
    public Object clone() throws CloneNotSupportedException 
    { 
        // Assign the shallow copy to new reference variable 
        // t 
        Test2 t = (Test2)super.clone(); 
  
        t.c = new Test(); 
  
        // Create a new object for the field c 
        // and assign it to shallow copy obtained, 
        // to make it a deep copy 
        return t; 
    } 
} 
  
public class Main { 
    public static void main(String args[]) 
        throws CloneNotSupportedException 
    { 
        Test2 t1 = new Test2(); 
        t1.a = 10; 
        t1.b = 20; 
        t1.c.x = 30; 
        t1.c.y = 40; 
  
        Test2 t3 = (Test2)t1.clone(); 
        t3.a = 100; 
  
        // Change in primitive type of t2 will not 
        // be reflected in t1 field 
        t3.c.x = 300; 
  
        // Change in object type field of t2 will not 
        // be reflected in t1(deep copy) 
        System.out.println(t1.a + " " + t1.b + " " + t1.c.x 
                           + " " + t1.c.y); 
        System.out.println(t3.a + " " + t3.b + " " + t3.c.x 
                           + " " + t3.c.y); 
    } 
}