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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<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()+””;
}
}
