Java的新手-返回单元测试失败

Question

Im working on a Java program in class and im unsure why or how this is failing considering I get the correct print out when the program is ran.

Here is the code I have:

import java.util.Scanner;

public class TextAnalyzer {

    // Create scanner

    private static Scanner scnr = new Scanner(System.in);
    // Create text string
    private static String text;

    public static void main(String[] args) {
        System.out.println("Enter a sentence or phrase: ");
        // Scan for text input
        text = scnr.nextLine();

        System.out.println("You entered: " + text);

        // Call getNumOfCharacters
        int count = getNumOfCharacters();
        System.out.println();
        System.out.println("Number of characters: " + count);
        // Call outputWithoutWhitespace
        String modifiedstring = outputWithoutWhitespace();
        System.out.println("String with no whitespace: " + modifiedstring);

    }

    // Method outputs string without spaces

    private static String outputWithoutWhitespace() {
        text = text.trim().replaceAll(" ", "");
        return text;
    }

    // Method to return number of characters

    private static int getNumOfCharacters() {
        return text.length();
    }
}

The output passes on all levels, it's the Unit test for the number of characters in the input that is failing and I really just need some guidance as a new student to Java programming.

Here is a printout of the tests:

My assumption is that the getNumOfCharacters() is returning the number of characters AFTER the whitespaces have been removed, but I could be wrong.

Any help/guidance would be greatly appreciated.

Answer 1

Your assumption is correct and the problem is that you are replacing text with the stripped text :

private static String outputWithoutWhitespace() {
    text = text.trim().replaceAll(" ", "");
    return text;
}

... and now getNumOfCharacters() is returning the stripped length, which is no longer eg 46.

That is, when you hit this line in main :

String modifiedstring = outputWithoutWhitespace();

It has the side-effect of replacing text , since that's precisely what you told outputWithoutWhitespace() to do. So by the time main ends, text now contains the modified text, and subsequent calls to getNumOfCharacters() fail the unit tests.

Your printed output is misleading (still prints "46") because you compute and store the character count before you mess up text in outputWithoutWhitespace() .

This is a good exercise in how to process and manage data, and a good learning experience for you. It's also a nice demonstration of the value of unit tests in quality control; you should remember this lesson.

Here's a hint: Based on your application requirements, does outputWithoutWhitespace() really need to store the trimmed text? Or does it just need to return it?

In the future, for debugging, consider:

• Stepping through in a debugger where possible to examine what's happening along the way.
• Adding diagnostic printouts, for example, print the value of text in getNumOfCharacters() to verify that it is what you think it is. Especially given your assumption that the problem was here and the failed unit test, this would be a good place to start investigating.