How Can I Instantiate Java Classes Using Only Their String Names?

Instantiating Classes by Name in Java

Java provides two methods to instantiate classes by passing their string name:

1. Using Reflection with a No-Arg Constructor

If the target class has a no-argument constructor, you can use the Class.forName() method to obtain the Class object. Subsequently, call the newInstance() method to create an instance:

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

2. Using Reflection for Classes with or without No-Arg Constructors

For a more comprehensive approach that works for classes with or without no-arg constructors, follow these steps:

1. Retrieve the Class object using Class.forName().
2. Obtain the constructor object using the getConstructor() method, specifying the parameter types if necessary.
3. Instantiate the class by invoking newInstance() on the constructor object, passing the required parameters.

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

Note: Both approaches involve reflection, which should be used judiciously as it can circumvent Java's exception handling and security constraints.

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