As the OP is a new beginner to programming, I would like to explain more.
You wil need this line on the top of your code in order to compile:
import java.util.Scanner;
This kind of import statement is very important. They tell the compile of which kind of Scanner you are about to use, because the Scanner here is undefined by anyone.
After a import statement, you can use the class Scanner directly and the compiler will know about it.
Also, you can do this without using the import statement, although I don't recommend:
java.util.Scanner scanner = new java.util.Scanner(System.in);
In this case, you just directly tell the compiler about which Scanner you mean to use.
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