JUnit测试方法失败

Question

I'm stuck on this simple JUnit testing method as I'm not sure how to pass this method that has iterator. If anyone can take a look that would be really helpful.

Here is main class:

public class Main {
    public static void main(String[] args) {

    final List<Integer> numbers = Arrays.asList(3, 4, 6, 1, 9);
    final Integer x = Integer.valueOf(1);
    System.out.println(findSame(numbers.iterator(), x, 0));
}
public static final int findSame(Iterator<Integer> iterator, Integer x, int idx) {
    if (!iterator.hasNext()) {
        return -1;
    }

    if (iterator.next().equals(x)) {
        return idx;
    } else {
        return findSame(iterator, x, idx+1);
    }
}

}

Here is my testing trial method, which is not functional. I'm having trouble with iterator mainly and how to pass these particular values in this testing method:

@Test
public void searchNumReturnsIndex1(){
    Main instance = new Main();        

    int x = 1;

    Iterator<Integer> iterator;
    int result = Main.findSame(null, x, 3);
    assertEquals(2, instance.findSame(null,x, 3));  
    }

Answer 1

Assuming you are doing this to practice passing an iterator as an argument, what you should do is this:

public class main {
    public static void main(String[] args) {
        // put whatever you want here, but if 'findSome' gets it's iterator as an argument,
        // then you shouldn't be trying to define it's list here. It's list is being passed
        // to it as an argument.
    }

    /* don't put final here unless you are working with subclasses and don't want them making their own versions of findSame */
    public static  int findSame(Iterator<Integer> iterator, Integer x, int idx) {
        if(!iterator.hasNext()) {
            return -1;
        }

        if(iterator.next().equals(x)) {
            return idx;
        } else {
            return findSame(iterator, x, idx+1);
        }
    }
}

And the test should be something like this:

@Test
public void searchNumReturnsIndex1() {
    Main instance = new Main();

    List<Integer> numbers = Arrays.asList(3, 4, 6, 1, 9);

    Iterator<Integer> iterator = numbers.iterator();

    int result = instance.findSame(iterator, 1, 3);
    assertEquals(2,result);
}

This should compile and test what your code was trying to test. There are some issues with your design though.

First, you shouldn't have findSame take that third argument, unless for some reason you want the ability to only check part of the list. Something like what's below will be more efficient, and the function will be simpler.

findSame(Iterator<Integer> iterator, Integer x) {
    while(iterator.hasNext()) {
        if(iterator.next().equals(x)) {
            return iterator.previousIndex();
        }
    }
    return -1;
}

Instead of thinking "findSome checks if this iterator contains this element at the given index or beyond" you can think "findSome checks if this iterator contains this element".

Second, you should always style your code consistently. You didn't indent your code consistently, findSame was indented the same amount as public class main , which made me think findSame was on the same level as the class main, not contained inside main.

Indenting should tell you about the structure of the program at a glance, so you don't have to read every detail of a program to get the general flow of it.

Answer 2

如果我对它的理解很好...'searchNum'函数将在'数字'列表中返回'x'的索引...在这种情况下，'6'位于第三位置（index = 2），因此您需要比较的价值：

 assertEquals(2, instance.searchNum(x, 0));

Answer 3

Change from

 assertEquals(1, instance.searchNum(x, 2));  

to

 assertEquals(2, instance.searchNum(x, 2));  

and then see whether it works or not. It will surely work if 6 is at second index of numbers array as you have mentioned in code above.