Why am i getting java.lang.illegalstateexception why i run my code yet it has no errors

Question

Import java.util.regex.Matcher;
Import java.util.regex.pattern;

public class RegularExpressionDemo{

public static void main(String[]args){
String s="I will be home in 10 minutes";
Pattern p=Pattern.compile("\\bin\\b");

Matcher m=p.matcher(s);

while(m.find());
System.out.println("pattern matches"+m.group()+"at"+m.start());

}
}

Answer 1

The problem is your while loop. You need to use curly brackets.

while(m.find());
If you use semicolon the loop has no body. Means you are calling m.group() and m.start() also when m.find() is not true.

Here is a correct code:

https://code.sololearn.com/ch2TqOpRcnXO/?ref=app

Answer 2

Hello John

About the exception:

"Signals that a method has been invoked at an illegal or inappropriate time. In other words, the Java environment or Java application is not in an appropriate state for the requested operation."

https://docs.oracle.com/javase/7/docs/api/java/lang/IllegalStateException.html

So you need to control all your method calls.

Answer 3

group() throws IllegalStateException - "If no match has yet been attempted, or if the previous match operation failed"

Answer 4

1st error: There shouldn't be a semi colon after youe while statement.

2nd error: Enclose the statements written after the while statement within curly brackets i.e. { }

Your final while statement should look like this:

while(m.find())
{
System.out.println("pattern matches"+m.group()+"at"+m.start())
}

Answer 5

I am using Eclipse to run my codes so when I fail to place a semi colon at the end of the loop it usually says that there is an error but after placing the semi colon there is no errors

Answer 6

'while' is like 'if' and 'for': it will run the code in between {} if condition matches.

while(numberOfUsers > 0) {
//do stuff as long as
//numberOfUsers is above zero
}

Placing ; after while will most likely make it check condition forever, resulting in some crash. At least it's easy to notice.
I'll add code example where accidentally added ; won't crash the code, but make output wrong. EDIT: here it is:
https://code.sololearn.com/cl1899qT2x5a/?ref=app

Answer 7

Thank you