How to make a java code which will take a PIN and if it's true, it will perform the functions of class A otherwise it will omit?

Answer 1

First, you will have to need some kind of input. This can be an alert-prompt, or an input-field. Then, when the user wants to continue, you could use an if-statement to check if the input contains the correct PIN. If the PIN is incorrect, you can return false and whatever message you'd like.

Answer 2

var pass= prompt("Enter Password");
if (pass == 0000) // replace "0000" with your desired password
{alert("allowed.");

//some code

}
else {alert("not allowed");
}