java中的ArrayList需要通過collections類的sort方法來進行排序
如果想自定義排序方式則需要有類來實現Comparator接口並重寫compare方法
調用sort方法時將ArrayList對象與實現Commparator接口的類的對象作爲參數
示例:
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class Test {
public static void main(String[] args) {
Student zlj = new Student("丁曉宇", 21);
Student dxy = new Student("趙四", 22);
Student cjc = new Student("張三", 11);
Student lgc = new Student("劉武", 19);
List<Student> studentList = new ArrayList<Student>();
studentList.add(zlj);
studentList.add(dxy);
studentList.add(cjc);
studentList.add(lgc);
Collections.sort(studentList, new SortByAge());
for (Student student : studentList) {
System.out.println(student.getName() + " / " + student.getAge());
}
System.out.println(" = ");
Collections.sort(studentList, new SortByName());
for (Student student : studentList) {
System.out.println(student.getName() + " / " + student.getAge());
}
}
}
class SortByAge implements Comparator {
public int compare(Object o1, Object o2) {
Student s1 = (Student) o1;
Student s2 = (Student) o2;
if (s1.getAge() > s2.getAge())
return 1;
return 0;
}
}
class SortByName implements Comparator {
public int compare(Object o1, Object o2) {
Student s1 = (Student) o1;
Student s2 = (Student) o2;
return s1.getName().compareTo(s2.getName());
}
}