问题描述
我有一个使用 Collections.sort 排序的 ArrayList.但结果如下所示.我如何让它按升序排列?
I have an ArrayList which I have sorted using Collections.sort.But the outcome looks like down below. How do I get it to be ascending order?
[0, 1, 11, 12, 12, 13, 13, 14, 14, 16, 16, 16, 17, 17, 17, 18, 18, 19, 2, 2, 20, 20, 20, 21, 21, 22, 4, 7, 7, 7, 8, 9, 9, 9, 9, 9]
推荐答案
看起来您的 ArrayList 包含字符串而不是数字.您可以通过传递自定义 Comparator 到 sort() 方法.
Looks like your ArrayList contains strings instead of numbers. You can sort it in numerical order by passing a custom Comparator to the sort() method.
在 java 8 中，您可以使用 Comparator.comparingInt() 做实际比较，结合Integer.parseInt() 方法执行从字符串到整数的转换:
In java 8, you can use Comparator.comparingInt() to do the actual comparision, in combination with the Integer.parseInt() method to perform the conversion from string to int:
ArrayList<String> list = new ArrayList<>();
// ... add values
list.sort(Comparator.comparingInt(Integer::parseInt));
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