string firstname="hassan";console.printf("my name is hassan",firstname);

String first name = "hassan"; < --- That's not right. This says create a String variable named first with .... ?

String firstName = "hassan"; <--- Says create a String variable with firtName as it's reference equal to Hassan

Perhaps you should watch the video again.

Your code should look like this:

String firstName = "Hassan";
console.printf("My name is %s", firstName);

Okay, now the explanation:

First of all, make sure you type String with capital S, this is important.

variables should not contain spaces first name is wrong. Also best practice is to write with camel cases (thisIsAnExampleForTypingInCamelCase), FYI, you can't name variables with numbers in the beginning (2ndName is bad, but name2 is okay)

After a semicolon, move down a line, that's also a best practice and makes your code look better and more understandable.

if you type "my name is Hassan" you are not using the variable so use the variable, not the plain text of your name.

The first thing I see is that you didn't capitalize the s in String. You must capitalize String for reasons to complicated to explain here.

Then your printf is a formatting print. So you need TWO arguments. So you need a string to print and a variable in which to use inside the string.

%s is a place holder within a string for some variable. For example

String variable = "cool";
console.printf("Something is %s", variable);

This returns

Something is cool.

You can put them on the same line but I wouldn't do that at this point.

Let me know if that clears it up for you!