Java似乎没有正确比较Doubles [英] Java doesn't seem to be comparing Doubles right

问题描述

我创建了一个链接列表，具有插入，搜索和删除功能。我也为它创建了一个迭代器。现在，假设我这样做：

I created a Linked List, with insert, search and remove functions. I also created a iterator for it. Now, suppose I do this:

myList<Integer> test = new myList();
test.insert(30);
test.insert(20);
test.insert(10);
myList.iterator it = test.search(20);
if(it.hasNext())
    System.out.println(it.next());

而且，它可以工作（它打印节点上元素的值，在这种情况下为20 ）。现在，如果我这样做：

And voila, it works (it prints the value of the element at the node, in this case 20). Now, if I do this:

myList<Double> test = new myList();
test.insert(30.1);
test.insert(20.1);
test.insert(10.1);
myList.iterator it = test.search(20.1);
if(it.hasNext())
    System.out.println(it.next());

它没有，因为迭代器指向null。这是搜索功能的实现：

It doesn't, because the iterator is pointing to null. Here is the implementation of the search function:

public iterator search(T data)
{
    no<T> temp = first;
    while( (temp != null) && (temp.data != data) )
        temp = temp.next;
    return (new iterator(temp));
}

以下是我如何知道有什么比较的东西：如果我更改部分上面的代码如下：

Here's how I know there's something fishy with the comparisons: If I change part of the above code like this:

while( (temp != null) && (temp.data != data) )
     System.out.println(temp.data + " " + data);
     temp = temp.next;

我可以看到它打印列表中的数字。它在一点打印20.1 20.1（例如）。那我该怎么解决呢？该函数似乎是正确的，但它似乎好像Java不正确比较数字。

I can see it printing the numbers in the list. It prints, at one point, "20.1 20.1" (for example). So how can I fix this? The function appears to be right, but it just seems as if Java isn't comparing the numbers correctly.

编辑：wth，BigDecimal也给了我同样的问题。

wth, BigDecimal gave me the same kind of problem too.

编辑2：等于（）工作，没有意识到别的东西是不幸的。对不起，

EDIT 2: equals() worked, didn't realize something else was amiss. Sorry.

推荐答案

你不需要这个！=操作符。它映射参考。你想要 .equals（）方法：

You don't want the != operator for this. It comapres references. You want the .equals() method:

public iterator search(T data)
{
    no<T> temp = first;
    while (!data.equals(temp.data)) {
        temp = temp.next;
    }
    return (new iterator(temp));
}

另外，注意自动拳击。您可能会发现 test.search（20.1）框20.1至浮动不是双，这可能会打破你的比较。将结果与 test.search（20.1d）进行比较。如果我记得正确，表达式：

Also, watch out for auto-boxing. You may find that test.search(20.1) boxes 20.1 to a Float not a Double, which will probably break your comparison. Compare the results with test.search(20.1d). If I recall correctly, the expression:

new Float(20.1).equals(new Double(20.1))

为假。

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