algorithm-class/算法新手班/class06/ShowComparator.java

package class06;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

public class ShowComparator {

	public static class Student {
		public String name;
		public int id;
		public int age;

		public Student(String name, int id, int age) {
			this.name = name;
			this.id = id;
			this.age = age;
		}
	}

	// 谁id大，谁放前！
	public static class IdComparator implements Comparator<Student> {

		// 如果返回负数，认为第一个参数应该排在前面
		// 如果返回正数，认为第二个参数应该排在前面
		// 如果返回0，认为谁放前面无所谓
		@Override
		public int compare(Student o1, Student o2) {
			if (o1.id < o2.id) {
				return 1;
			} else if (o2.id < o1.id) {
				return -1;
			} else {
				return 0;
			}
		}
	}
	
	// 谁age大，谁放前！
	public static class AgeComparator implements Comparator<Student> {

		// 如果返回负数，认为第一个参数应该排在前面
		// 如果返回正数，认为第二个参数应该排在前面
		// 如果返回0，认为谁放前面无所谓
		@Override
		public int compare(Student o1, Student o2) {
			if (o1.age < o2.age) {
				return 1;
			} else if (o2.age < o1.age) {
				return -1;
			} else {
				return 0;
			}
		}
	}

	public static void printArray(int[] arr) {
		for (int i = 0; i < arr.length; i++) {
			System.out.print(arr[i] + " ");
		}
		System.out.println();
	}

	public static void printStudents(Student[] students) {
		for (int i = 0; i < students.length; i++) {
			System.out.println(students[i].name + ", " + students[i].id + ", " + students[i].age);
		}
	}

	public static void main(String[] args) {
		int[] arr = { 8, 1, 4, 1, 6, 8, 4, 1, 5, 8, 2, 3, 0 };
		printArray(arr);
		Arrays.sort(arr);
		printArray(arr);

		Student s1 = new Student("张三", 5, 27);
		Student s2 = new Student("李四", 1, 17);
		Student s3 = new Student("王五", 4, 29);
		Student s4 = new Student("赵六", 3, 9);
		Student s5 = new Student("左七", 2, 34);

		Student[] students = { s1, s2, s3, s4, s5 };
		printStudents(students);
		System.out.println("=======");
		Arrays.sort(students, new IdComparator());
		printStudents(students);
		System.out.println("=======");

		ArrayList<Student> arrList = new ArrayList<>();
		arrList.add(s1);
		arrList.add(s2);
		arrList.add(s3);
		arrList.add(s4);
		arrList.add(s5);
		for (Student s : arrList) {
			System.out.println(s.name + ", " + s.id + ", " + s.age);
		}
		System.out.println("=======");
		arrList.sort(new AgeComparator());
		for (Student s : arrList) {
			System.out.println(s.name + ", " + s.id + ", " + s.age);
		}

	}

}