Question

Basically, I am trying to do a while loop, and to keep reading until the line input is $. When that is read, the the loop should exit.

However I am getting a runtime exception as java.util.InputMismatchException.

Here is the code:

while (scan.nextLine() != "$") {
    temp1 = scan.nextInt();
    temp2 = scan.nextInt();
    addEdge(temp1, temp2);
}

Answer 1

You need to use the line you read in (inside the while condition).

When you call nextLine() you not only are checking if it equals “$” but also you are throwing it away.

I assume you are reading input that is like the following: (I bet you are)

1 2
3 4
0 1
4 5
$

try the following:

String nextLineStr;
while( !((nextLinestr = scan.nextLine()).equals("$")))
{
String tokens [] = nextLineStr.split(" ");
temp1 = Integer.parseInt(tokens[0]);
temp2 = Integer.parseInt(tokens[1]);
addEdge(temp1,temp2);
}

As a side note: Notice that I switched out your ‘!=’ for a not equals method, this is because a String should not be compared using == or !=