集合框架-ArrayList集合儲存自定義物件的排序案例

(4)案例

A:ArrayList集合儲存自定義物件的排序

package cn.itcast_02;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/*
 * Collections可以針對ArrayList儲存基本包裝類的元素排序，儲存自定義物件可不可以排序呢?
 */
public class CollectionsDemo {
	public static void main(String[] args) {
		// 建立集合物件
		List<Student> list = new ArrayList<Student>();

		// 建立學生物件
		Student s1 = new Student("林青霞", 27);
		Student s2 = new Student("風清揚", 30);
		Student s3 = new Student("劉曉曲", 28);
		Student s4 = new Student("武鑫", 29);
		Student s5 = new Student("林青霞", 27);

		// 新增元素物件
		list.add(s1);
		list.add(s2);
		list.add(s3);
		list.add(s4);
		list.add(s5);

		// 排序
		// 自然排序
		// Collections.sort(list);
		// 比較器排序
		// 如果同時有自然排序和比較器排序，以比較器排序為主
		Collections.sort(list, new Comparator<Student>() {
			@Override
			public int compare(Student s1, Student s2) {
				int num = s2.getAge() - s1.getAge();
				int num2 = num == 0 ? s1.getName().compareTo(s2.getName()): num;
				return num2;
			}
		});

		// 遍歷集合
		for (Student s : list) {
			System.out.println(s.getName() + "---" + s.getAge());
		}
	}
}

package cn.itcast_02;

/**
 * @author Administrator
 * 
 */
public class Student implements Comparable<Student> {
	private String name;
	private int age;

	public Student() {
		super();
	}

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

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	@Override
	//這是自然排序
	public int compareTo(Student s) {
		int num = this.age - s.age;
		int num2 = num == 0 ? this.name.compareTo(s.name) : num;
		return num2;
	}
}