如何在Java中按两个字段排序? [英] How to sort by two fields in Java?
问题描述
我有对象数组 person(int age; String name;)
。
我如何排序这个数组按名称按字母顺序排列,然后按年龄排列?
How can I sort this array alphabetically by name and then by age?
你会使用哪种算法?
推荐答案
您可以使用 Collections.sort
,如下所示:
You can use Collections.sort
as follows:
private static void order(List<Person> persons) {
Collections.sort(persons, new Comparator() {
public int compare(Object o1, Object o2) {
String x1 = ((Person) o1).getName();
String x2 = ((Person) o2).getName();
int sComp = x1.compareTo(x2);
if (sComp != 0) {
return sComp;
}
Integer x1 = ((Person) o1).getAge();
Integer x2 = ((Person) o2).getAge();
return x1.compareTo(x2);
}});
}
列表<人员>
现在按名称排序,然后按年龄排序。
List<Persons>
is now sorted by name, then by age.
String.compareTo
按字典顺序比较两个字符串 - 来自文档。
String.compareTo
"Compares two strings lexicographically" - from the docs.
Collections.sort
是本机Collections库中的静态方法。它进行实际的排序,你只需要提供一个Comparator,它定义了列表中两个元素的比较方式:这是通过提供你自己的 compare
方法的实现来实现的。 。
Collections.sort
is a static method in the native Collections library. It does the actual sorting, you just need to provide a Comparator which defines how two elements in your list should be compared: this is achieved by providing your own implementation of the compare
method.
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