Why can't the main method of a java class use the this keyword?

Static methods belong to the class, they will be loaded into memory with the class. You can call them without creating an object. (Use the class name as a reference).

Example

public class Sample{
　　　static int num =　50;
　　　public static void demo(){
　　　　　　System.out.println("Content of the static method");
　　　}
　　　public static void main(String args[]){
　　　　　　Sample.demo();
　　　}
}

Output result

Content of the static method

The keyword 'this' is used as a reference to the instance. Since static methods do not belong to any instance, they cannot use 'this' reference in static methods. If it still does, please try this, which will generate a compile-time error.

And the main method is static, so you cannot use 'this' to refer in the main method.

Example

public class Sample{
　　　int num =　50;
　　　public static void main(String args[]){
　　　　　　System.out.println("main method content"+this.num);
　　　}
}

Compile-time error

Sample.java:4: error: non-static variable this cannot be referenced from a static context
　　　System.out.println("Contents of the main method"+this.num);
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　^
1　error