List集合按某个字段排序

时间:2021-12-20 13:08:29
package wjtest_01;

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

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

List<Student> list = new ArrayList<Student>();

// 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<Student>() {

@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<Student>() {

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()+"";
}
}