集合转文件（字符流），文本文件中的信息读取到新的集合中（学生年龄降序排列）

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import java.util.Objects;
public class Student {
private String name;
private String sex;
private int age;
private
String score;
public Student() {
}
public Student(String name, String sex, int age, String score) {
this.name = name;
this.sex = sex;
this.age = age;
this.score = score;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getScore() {
return score;
}
public void setScore(String score) {
this.score = score;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + ''' +
", sex='" + sex + ''' +
", age='" + age + ''' +
", score='" + score + ''' +
'}';
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Student student = (Student) o;
return age == student.age &&
Objects.equals(name, student.name) &&
Objects.equals(sex, student.sex) &&
Objects.equals(score, student.score);
}
@Override
public int hashCode() {
return Objects.hash(name, sex, age, score);
}
}

1
创建Demo类代码示例：

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package demo01;
import java.io.*;
import java.util.*;
class AgeComparator implements Comparator<Student> {
//比较器 Comparator,按照学生年龄降序(从大到小)
//如果升序就o1.getage()-o2.getAge()（从小到大）
@Override
public int compare(Student o1, Student o2) {
return o2.getAge() - o1.getAge();
}
}
public class Demo {
public static void main(String[] args) throws IOException {
ArrayList<Student> studentArrayList = new ArrayList<>();
Student student1 = new Student("刘德华", "男", 22, "89");
Student student2 = new Student("成龙", "男", 19, "99");
Student student3 = new Student("张三", "男", 18, "99");
Student student4 = new Student("李四", "男", 21, "99");
Student student5 = new Student("王五", "男", 25, "99");
studentArrayList.add(student1);
studentArrayList.add(student2);
studentArrayList.add(student3);
studentArrayList.add(student4);
studentArrayList.add(student5);
Collections.sort(studentArrayList, new AgeComparato());
BufferedWriter bw = new BufferedWriter(new FileWriter("student.txt"));
for (Student s : studentArrayList
) {
bw.write(s.getName() + "，" + s.getSex() + "，" + s.getAge() + "，" + s.getScore());
bw.newLine();
bw.flush();
}
System.out.println("写入成功");
BufferedReader br = new BufferedReader(new FileReader("student.txt"));
ArrayList<String> arrayList = new ArrayList<>();
String line;
while ((line = br.readLine()) != null) {
arrayList.add(line);
}
br.close();
for (String s : arrayList
) {
System.out.println(s);
}
}
}

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class Student {
private String name;
private int age;
private int score;
}
//年龄比较器（从小到大）
class AgeComparator implements Comparator<Student> {
@Override
public int compare(Student o1, Student o2) {
return o1.getAge() - o2.getAge();
//年龄由大到小排序 ：return o2.getAge()-o1.getAge();
}
}
//成绩比较器
class ScoreComparator implements Comparator<Student> {
@Override
public int compare(Student o1, Student o2) {
return o1.getScore() - o2.getScore();
//成绩由大到小排序：return o2.getScore()-o1.getScore();
}
}
​
public class Demo04Comparator {
public static void main(String[] args) {
//创建学生对象，添加到集合当中
​
List<Student> students = new ArrayList<>();
​
students.add(new Student("小龙",22,97));
​
students.add(new Student("小明",15,86));
​
students.add(new Student("小花",26,100));
​
//按年龄从小到大对集合的学生对象进行排序
​
Collections.sort(students, new AgeComparator());
System.out.println(students);
​
//按分数从低到高对集合中的学生对象进行排序进行排序
​
Collections.sort(students, new ScoreComparator());
​
System.out.println(students);
​
}
​
}