Java 常用类库 之 比较接口 Comparator
http://www.verejava.com/?id=169931036202101 /** 知识点： 比较类 Comparator 题目: 将某班学生按数学成绩从小到大排序 思路: 1. 抽象出类: 1.1 班级(ClassSet) 1.2 学生(Student) 2. 找出类关系: 2.1 学生 属于 班级 Student -> ClassSet(多对1) 3. 找出类属性: 3.1 ClassSet(班级名称,班级人数) 3.2 Student(学生名称,数学成绩) 4. 找出类方法: 4.1 学生添加到班级 ClassSet{addStudent(Student s)} 4.2 学生成绩从小到大排序 ClassSet{sortByScore()} */ import java.util.Arrays; import java.util.Comparator; public class TestComparator { public static void main(String[] args) { //实例化4G班级 ClassSet c = new ClassSet("4G", 4); //添加学生 c.addStudent(new Student("李明", 90)); c.addStudent(new Student("李浩", 80)); c.addStudent(new Student("王涛", 95)); c.addStudent(new Student("张胜", 70)); //获得4G班级学生数组集合 Student[] students = c.getStudents(); //输出学生信息 for (Student s : students) { if (s != null) System.out.println(s.getName() + "," + s.getMathScore()); } System.out.println("\n根据学生成绩升序排序"); Arrays.sort(students, new StudentAscComparator()); for (Student s : students) { if (s != null) System.out.println(s.getName() + "," + s.getMathScore()); } System.out.println("\n根据学生成绩降序排序"); Arrays.sort(students, new StudentDescComparator()); for (Student s : students) { if (s != null) System.out.println(s.getName() + "," + s.getMathScore()); } } } class ClassSet { private String className;//班级名称 private int maxSize;//班级学生人数 private int currentSize;//当前多少学生 private Student[] students;//所有学生的数组 public ClassSet(String className, int maxSize) { this.className = className; this.maxSize = maxSize; students = new Student[maxSize]; } public Student[] getStudents() { return this.students; } /** 添加学生 */ public void addStudent(Student s) { for (int i = 0; i < students.length; i++) { if (students[i] == null) { students[i] = s; currentSize++; break; } } } } class Student { private String name;//学生姓名 private int mathScore;//数学成绩 public Student(String name, int mathScore) { this.name = name; this.mathScore = mathScore; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public int getMathScore() { return this.mathScore; } public void setMathScore(int mathScore) { this.mathScore = mathScore; } } /** 学生升序排列 */ class StudentAscComparator implements Comparator { public int compare(Object o1, Object o2) { if ((o1 instanceof Student) && (o2 instanceof Student)) { Student s1 = (Student) o1; Student s2 = (Student) o2; if (s1.getMathScore() > s2.getMathScore()) return 1; if (s1.getMathScore() < s2.getMathScore()) return -1; } return 0; } } /** 学生降序排列 */ class StudentDescComparator implements Comparator { public int compare(Object o1, Object o2) { if ((o1 instanceof Student) && (o2 instanceof Student)) { Student s1 = (Student) o1; Student s2 = (Student) o2; if (s1.getMathScore() > s2.getMathScore()) return -1; if (s1.getMathScore() < s2.getMathScore()) return 1; } return 0; } } http://www.verejava.com/?id=169931036202101
