how to properly get every line containing a specific word in java

I'm trying to write a program that reads a file and checks every line that contains a specific word then prints it.if there isn't one it should print "no match for your search".this is what I've got so far and and I'm having trouble putting it all together.after all my twinkering around and replacing thewhile with ifor putting the second if statement outside of the while, sometimes it doesn't matter what i enter it always says "no match for your search" and sometimes it says java.util.NoSuchElementException: No line found. and sometimes it freezes and i searched this up and it says its a bug in cmd or something.any help will be appreciated
and I'm new to java so please any thing you can advise me will be helpful and appreciated

System.out.println("search for book");
 
String search = scan.next();	
scan.nextLine();	

File file = new File("library.txt");
Scanner in = null;
in = new Scanner(file);
          
String line = in.nextLine();
while(in.hasNext()) {
    if(line.contains(search)) {
	    System.out.println(line);
	} 	
		   
    if(!line.contains(search)) {
		System.out.println("no match for your search");
		System.exit(0);
	}
}

Not mentioning logical errors in your code, you should probably create logical (boolean) variable outside of the loop and set it to false. If you encounter your condition, set it to true.
After the while loop, check the value. If it's false, that means no lines were found and you should print your message.

Example:

boolean foundAnything = false;
while(...) {
    ...
    if(condition) {
        foundAnything = true;
        ...
    }
    ...
}

// Nothing was found
if(!foundAnything) {
    ...
}

> sometimes it doesn't matter what i enter it always says "no match for your search"

The biggest issue here is this part inside your loop:

while(in.hasNext()) {
    if(line.contains(search)) {
        System.out.println(line);
    }   
           
    if(!line.contains(search)) {
        System.out.println("no match for your search");
        //HERE!!!
        System.exit(0);
    }
}

System.exit(0) will stop the program and nothing else will be executed. So if the search word is not found in the line, the program finishes.

> sometimes it says java.util.NoSuchElementException: No line found

You read the first line before the loop and maybe you have an empty file.

File file = new File("library.txt");
Scanner in = null;
in = new Scanner(file);

//this reads the first line of the file
String line = in.nextLine();
while(//rest of code...

You can overcome these two issues by:

• Read the contents of the file only in the loop
• Use a flag to check if the word was found
• Stop the loop only if the word was found OR if the file has no more lines
• In the loop, if the word is not found yet, just let it continue
• Avoid using System#exit unless really needed
• If after the loop the word was not found, print a message

With these suggestions in mind, your code can be designed like this:

File file = new File("library.txt");
Scanner in = new Scanner(file);

//Use a flag to check if the word was found 
boolean found = false;

//Stop the loop only if the word was found OR if the file has no more lines
while (!found && in.hasNextLine()) {
    //Read the contents of the file only in the loop
    String line = in.nextLine();
    if (line.contains(search)) {
        found = true;
        System.out.println(line);
    }
    //In the loop, if the word is not found yet, just let it continue
}
//If after the loop the word was not found, print a message
if (!found) {
    System.out.println("no match for your search");
}

First of all you seem to skip your first line. Secondly, second if clause is redundant.

Boolean found=false;
while(in.hasNext()) {
    String line = in.nextLine();
    if(line.contains(search)) {
        System.out.println(line);
        found=true;
    }           
}

if(found==false) System.out.println("no match for your search");