如何从Java中的数据数组中删除最少的项目？

Question

I am working on a homework assignment in which I need to write a method that takes a data array and removes the minimum item from it. I am able to find the minimum item, but I am having trouble removing it. My code is below.

  public Comparable removeMin() {

    Iterator<T> it = iterator();
    T min = it.next();
    while (it.hasNext()) {
        T next = it.next();
        if (min.compareTo(next) > 0)
            min = next;
        it.remove();

    }
    System.out.println(min);
    return min;
}

I have the print statement there just to verify that it is in fact getting the minimum item.

The code in main looks like this.

public static void main(String[] args) {

  Bag<String> sbag = new Bag<String>();

    sbag.add("Noriko");
    sbag.add("Peter"); 
    sbag.add("Buddy");
    sbag.add("Mary");

    sbag.removeMin();

  }

When I run the sbag.removeMin(); command, the console prints "Buddy" which tells me that it is choosing "Buddy" as the min item. However, if I instead populate sbag with integers, it always prints the smallest integer, which indicates to me I have my code correct in that regard.

I have two questions.

1). When passing a list of strings such as above, how does Java determine which is smallest?

2). How can I fix my code so that it not only finds the minimum item, but also removes it?

Answer 1

First, it compares String based on the integral value of the characters in the String (eg ASCII) (but it does that because String implements Comparable<String> ). I think you meant to return the generic type T , and you should check for an empty Collection . Finally, you need to iterate twice. Once to find the min the second to remove it.

public T removeMin() {
    Iterator<T> it = iterator();
    T min = (it.hasNext()) ? it.next() : null;
    while (it.hasNext()) {
        T next = it.next();
        if (min.compareTo(next) > 0) {
            min = next;
        }
    }
    it = iterator(); // <-- start again
    while (it.hasNext()) {
        T next = it.next();
        if (min.compareTo(next) == 0) {
            it.remove();
            break;
        }
    }
    System.out.println(min);
    return min;
}

Answer 2

It's using the ASCII code. In numeric byte values, B is lower in value than anything else you've got there.

Andto get rid of it, use array[n]="";