Thread: nested do while loop

I am very new at java and just trying to learn it on my spare time and I'm doing do-while loops and I am having trouble understanding the below code if somebody could help me out that would be great.

public class help {
public static void main (String args[])
throws java.io.IOException {
char choice, ignore;
do{
System.out.println ("Choose one:");
System.out.println("1. if");
System.out.println("2.switch");
 
choice = (char) System.in.read();
do{
ignore = (char) System.in.read();
}while(ignore != '\n');	
}while (choice < '1'| choice >'2');
 
switch(choice){
case '1': 
System.out.println("if");
break;
case '2':
System.out.println("switch");
break;
}
}
}

Whats the point of the block?

do{
ignore = (char) System.in.read();
}while(ignore != '\n');

It makes no difference in the program wither i delete this block or keep it

Also can somebody explain how while (choice < '1'| choice >'2'); translates? I would assume it would be while (choice >= '1'| choice =<'2');?

I'm not sure, I am just following a book and they said that that block get rids of unwanted characters? I dont see how it does that.

please explain things to me in simple terms, I am a mechanical engineer, I have little to no experience with coding.

With regards to the code block in question, you can see for yourself what it does by printing out "ignore", e.g.,

ignore = (char) System.in.read();
System.out.println("[" + ignore + "]");

To find out whether it is functionally useful, run the program (with the println statement in), enter "301" and observe the output. Stop the program (by typing 1 or 2, or press Ctrl-C). Remove the code block. Re-run the program, enter "301", and observe the difference in the output.