List集合按某个字段排序

package wjtest_01;

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

public class ListSort {
	@SuppressWarnings("unchecked")
	public static void main(String[] args) {

		List list = new ArrayList();

		// 创建3个学生对象，年龄分别是20、19、21，并将他们依次放入List中
		Student s1 = new Student();
		s1.setAge(20);
		s1.setUsable(true);
		Student s2 = new Student();
		s2.setAge(19);
		s2.setUsable(true);
		Student s3 = new Student();
		s3.setAge(21);
		s3.setUsable(false);
		list.add(s1);
		list.add(s2);
		list.add(s3);

		System.out.println("排序前：" + list);
		Collections.sort(list, new Comparator() {

			@Override
			public int compare(Student o1, Student o2) {
				// 按照学生的年龄进行升序排列
				if (o1.getAge() > o2.getAge()) {
					return 1;
				}
				if (o1.getAge() == o2.getAge()) {
					return 0;
				}
				return -1;
			}
		});

		System.out.println("升序排序后：" + list);

		Collections.sort(list, new Comparator() {

			public int compare(Student o1, Student o2) {

				// 按照学生的年龄进行降序排列
				if (o1.getAge() > o2.getAge()) {
					return -1;
				}
				if (o1.getAge() == o2.getAge()) {
					return 0;
				}
				return 1;
			}
		});

		System.out.println("降序排序后：" + list);

		Boolean b1 = true; // 创建Boolean对象1

		Boolean b2 = false; // 创建Boolean对象0

		Boolean b3 = true; // 创建Boolean对象1
		System.out.println(b1);

		int i;

		i = b1.compareTo(b2); // b1和b2进行比较  

		System.out.println(i);//1-0 

		i = b2.compareTo(b1); // b2和b1进行比较

		System.out.println(i);//0-1

		i = b1.compareTo(b3); // b1和b3进行比较

		System.out.println(i);//1-1
	}
}

class Student{  
    
    private int age;
    
    private Boolean isUsable;

	public int getAge() {  
        return age;  
    }  
  
    public Boolean isUsable() {
		return isUsable;
	}

	public void setUsable(Boolean isUsable) {
		this.isUsable = isUsable;
	}

	public void setAge(int age) {  
        this.age = age;  
    }  
    @Override  
    public String toString() {  
        return getAge()+"";  
    }  
}