java 创建对象的5种方法

╰+哭是因爲堅強的太久メ 2022-05-26 03:37 203阅读 0赞

**java 创建对象的5种方法**

**参考文章：https://www.cnblogs.com/wxd0108/p/5685817.html**

**其中调用构造函数方法有三种：**

**（1）使用new关键字 **

**（2）使用Class类的newInstance方法 **

**（3）使用Constructor类的newInstance方法 **

**没有调用构造函数两种：**

**（4）使用clone方法**

**（5）使用反序列化**

public static void main(String... args) throws Exception {
            // By using new keyword
            Employee emp1 = new Employee();
            emp1.setName("Naresh");
            System.out.println(emp1 + ", hashcode : " + emp1.hashCode());
    
            System.out.println("==========================================================================================");
    
            // By using Class class's newInstance() method
            Employee emp2 = (Employee) Class.forName("TestDemo.Employee")
                    .newInstance();
            // Or we can simply do this
             Employee emp22 = Employee.class.newInstance();
            emp22.setName("hello Spark !");
            emp2.setName("Rishi");
            System.out.println(emp22 +", hashcode : " + emp22.hashCode());
            System.out.println(emp2 + ", hashcode : " + emp2.hashCode());
            System.out.println(emp1 + ", hashcode : " + emp1.hashCode());
            System.out.println("==========================================================================================");
            // By using Constructor class's newInstance() method
            Constructor<Employee> constructor = Employee.class.getConstructor();
            Employee emp3 = constructor.newInstance();
            emp3.setName("Yogesh");
            System.out.println(emp3 + ", hashcode : " + emp3.hashCode());
            System.out.println(emp1 + ", hashcode : " + emp1.hashCode());
            System.out.println("==========================================================================================");
            // By using clone() method
            Employee emp4 = (Employee) emp3.clone();
            emp4.setName("Atul");
            System.out.println(emp4 + ", hashcode : " + emp4.hashCode());
            System.out.println(emp3 + ", hashcode : " + emp3.hashCode());
            System.out.println("==========================================================================================");
            // By using Deserialization
            // Serialization
            ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("data.obj"));
            out.writeObject(emp4);
            out.close();
            //Deserialization
            ObjectInputStream in = new ObjectInputStream(new FileInputStream("data.obj"));
            Employee emp5 = (Employee) in.readObject();
            in.close();
            emp5.setName("Akash");
            System.out.println(emp5 + ", hashcode : " + emp5.hashCode());
            System.out.println(emp4 + ", hashcode : " + emp4.hashCode());
            System.out.println("==========================================================================================");
        }