Class Class in Java

What is Class Class in Java?

java.lang.Class is one of the most important classes in Java and it has many useful methods which are used in Application development like isArray(), isEnum(), etc. They are popularly used for loading Oracle or MySQL drivers in the Java application.

It also provides methods like Class.newInstance() which is the backbone of the reflection class present in Java and it helps us in creating an instance of a class without using the new() operator unlike for other classes. The Class class present in Java has a private constructor, so a new keyword does not help in creating the instance of it, instead of it we use three methods for creating the object of the class. And also the class instance is created by JVM at Runtime when a class is loaded. The object of class Class is also used to represent classes, enum, interfaces, and annotations in a running Java application. java.lang.class is a final class so it cannot be inherited into other classes.

The primitive data types like byte, short, char, int, float, and boolean are also represented using these Class instances.

For example:

String str = "strings";

Class c = Integer.class;

In the above instance, we see that "strings" are stored as a string data type in the application but whereas Integer is stored as a class type in the program which is referenced by the variable of class type c. Using c we can create an object for the Integer class. We can get the details about that class dynamically even during Runtime.

Class present in Java is also used to represent an instance of the array in Java.

Three Ways to Create a Class object in Java

As we have discussed earlier, the Class class has a private constructor so it cannot be called or created outside the class (globally), so to avoid that we mainly have three ways of instantiating the object of the Class class in Java. They are discussed in this section:

1. Using Class.forName(): This internally uses Class loader support to load the class.

For example:

Class c = Class.forName("java.util.Date")

This Class.forName method loads java.util.Date class and returns the object of java.lang.Class having loaded class name as the data of the object. Here c is the reference variable pointing to the object of java.lang.Class. The below image clearly explains the memory diagram of the instantiated class: 2. Using getClass() method of java.lang.Object class. This method can be used on any class because it is invokable on any class object.

For example:

button b = new button();

Class c = b.getClass();

The button is the data of the object which is the object of java.lang.Class. C is the reference variable for the object of the java.lang.Class. The below image clearly explains the memory diagram of the instantiated class: 3. Using Myclass.class writing .class after a class name, helps in referencing the Class object which represents the given class. It is frequently used with primitive and also non-primitive data types. This method is used only when the name of the class is known before creating the object. The class name for which the Class object is to be created is determined at compile time.

For example:

$~~~~~~~~$ Solution s = new Solution()

$~~~~~~~~$ Class c = Solution.class()

This statement does not give any error because it is instantiated with the Solution class.

Methods of Class Class in Java

This section explains a few methods present in Class class in Java with the method name, syntax, and description:

Examples of Class Class in Java

Below is the Java program which helps in practical understanding of the above-mentioned methods present in Class class present java.lang package:

Output:

The second example of Java implementation to mention all the different methods mentioned above is:

Output: