How to instantiate in java?

In Java, using a defined class, the process of creating an object of this class is called "instantiation". Instantiation is the process of allocating memory in the heap, and the allocated memory is the object. Only the instantiated object can access the member variables and methods in the class. (Recommendation: java video tutorial)

Let’s take a look at the method of instantiating java objects:

1) Use the new () of the class to create

User user = new User();

2) Use the clone method to create, the class needs to implement the Cloneable interface

User user2 = (User) user1.clone();

3) Use the Class.forName method to get the class, and call the newinstance() method of the class

Class<?> cls =null;
User u = null;
try {
cls = Class.forName("com.dao.User");
u = (User)cls.newInstance();
} catch (ClassNotFoundException e1) {
e1.printStackTrace();
}

4) After instantiating an object, serialize it, and then deserialize it, you can also get an object (used in remote communication scenarios)

try{
ObjectOutputStream out = new ObjectOutputStream (new FileOutputStream("D:/objectUser.txt"));
//序列化对象
out.writeObject(user1); //"Kong zi", "13800010001", "Greatwalk"
out.close();
//反序列化对象
ObjectInputStream in = new ObjectInputStream(new FileInputStream("D:/objectUser.txt"));
User user4 = (User) in.readObject();
System.out.println("反序列化user：" + user4);
in.close();
}
catch(ClassNotFoundException e ){
e.printStackTrace();
}
catch(FileNotFoundException e ){
e.printStackTrace();
}
catch(IOException e ){
e.printStackTrace();
}

For more java knowledge, please pay attention java basic tutorial column.

The above is the detailed content of How to instantiate in java?. For more information, please follow other related articles on the PHP Chinese website!