死代码Java Eclipse

Question

I am trying to check if the word given by the user already exists in the text file or a substring of it already exists. Here's my code:

String ans = null;
Scanner scanner = null;
do
{
    System.out.print("Please enter a new word: ");
    String Nword = scan.next();
    System.out.print("And its appropriate Hint: ");
    String Nhint = scan.next();

    Word word = new Word(Nword , Nhint);
    File file = new File("C:\\Users\\Charbel\\Desktop\\Dictionary.txt");
    file.createNewFile();
    scanner = new Scanner(file);
    if (scanner != null)
    {
        String line;
        while (scanner.hasNext()) {
            line = scanner.next();
            for(int i = 0 ; i<line.length(); i++)
                if ((line.equals(Nword)) || (Nword.equals(line.substring(i))))
                {
                    System.out.println("The word already exists.");
                    break;
                }
        }
    }
    else
    {
        FileWriter writer = new FileWriter(file , true);
        writer.write(word.toString());
        writer.write(System.lineSeparator());
        writer.flush();
        writer.close();

        System.out.println("Your word has successfuly added.");
        System.out.print("\nWould you like to add another word ?\nPress 0 to continue.");
        ans = scan.next();
    }
} while(ans.equals("0"));

Eclipse said that the statements after the else condition are "Dead Code" and I don't know why.

Answer 1

scanner = new Scanner(file);

scanner is initialized, can never be null , so the else statement will never be reached.

See the constructor :

Throws:
FileNotFoundException - if source is not found

So if the file doesn't exists, scanner won't be null , you'll have an exception .

Answer 2

scanner = new Scanner(file);

This statement is creating a new instance here. So this: if (scanner != null) will never be false.

Answer 3

Dead-Code is which never gets executed, for example:

if(true) {
// do something
}else {
// do something else <-- this is dead code, or else-block is dead code
}

In your case since Scanner is getting created before if(scanner != null) there is no way of execution of associated else . If Scanner creation fails error will be thrown again in which else will not be executed, hence from compiler point-of-view no chance of else block getting executed hence dead-code .

if-else would have made sense if scanner instance is passed as argument.

To solve this, else should be removed!

Following should correct your code:

                scanner = new Scanner(file);
                FileWriter writer = new FileWriter(file, true);
                if (scanner != null) {
                    String line;
                    while (scanner.hasNext()) {
                        line = scanner.next();
                        for (int i = 0; i < line.length(); i++)
                            if ((line.equals(""))
                                    || ("".equals(line.substring(i)))) {
                                System.out.println("The word already exists.");
                                break;
                            } else {
                                writer.write(word.toString());
                                writer.write(System.lineSeparator());
                                writer.flush();
                                System.out.println("Your word has successfuly added.");
                                System.out.print("\nWould you like to add another word ?\nPress 0 to continue.");
                                ans = scan.next();
                            }
                    }
                }
                writer.close();