How Can I Instantiate Java Classes by Name Only?

Instantiating Classes by Name in Java

Some situations require the instantiation of a class using only its name. This guide will explore two methods to achieve this in Java.

Method 1: For Classes with No-arg Constructors

Assuming the class possesses a no-arg constructor, utilize Class.forName() to obtain a Class object representing the class. Then, employ the newInstance() method to create an instance. Note that this method is commonly discouraged as it can circumvent Java's checked exceptions.

Example:

Class> clazz = Class.forName("java.util.Date");
Object date = clazz.newInstance();

Method 2: General Approach

For classes with or without no-arg constructors, utilize a safer approach that involves retrieving a Constructor object from the class object and invoking its newInstance() method.

Example:

Class> clazz = Class.forName("com.foo.MyClass");
Constructor> constructor = clazz.getConstructor(String.class, Integer.class);
Object instance = constructor.newInstance("stringparam", 42);

Note:

Both methods leverage reflection, a versatile technique that enables dynamic inspection of classes and objects. However, it is essential to handle potential exceptions, including those related to class resolution, constructor availability, and security restrictions imposed by the Java virtual machine or security manager.

The above is the detailed content of How Can I Instantiate Java Classes by Name Only?. For more information, please follow other related articles on the PHP Chinese website!