说说Comparator比较器那些用法

importlombok.Data;
@DatapublicclassStudent {
/** 姓名 */privateStringname;
/** 年龄 */privateIntegerage;
/** 成绩 */privateDoublescore;
/** 是否优秀学生 */privateBooleanmerit;
}

privatestaticintgetRandomAge() {
Randomrandom=newRandom();
returnrandom.nextInt(3) +16;
}

privatestaticdoublegetRandomScore() {
Randomrandom=newRandom();
doublea=random.nextDouble() *100;
DecimalFormatdf=newDecimalFormat("0.00");
Stringstr=df.format(a);
returnDouble.parseDouble(str);
}

privatestaticbooleangetRandomMerit() {
Randomrandom=newRandom();
returnrandom.nextBoolean();
}

privatestaticList<Student>getStudentList() {
List<Student>list=newArrayList<>();
Stringname="张";
for (inti=1; i<=5; i++) {
Studentstudent=newStudent();
// 姓名拼接student.setName(name+i);
student.setAge(getRandomAge());
// 设置缺考成绩if (i==2||i==3) {
student.setScore(null);
        } else {
student.setScore(getRandomScore());
        }
student.setMerit(getRandomMerit());
list.add(student);
    }
returnlist;
}

List<Student>studentList=getStudentList();
// 进行年龄排序-正序studentList.sort(Comparator.comparingInt(Student::getAge));
// 排序-倒序studentList.sort(Comparator.comparingInt(Student::getAge).reversed());

List<Student>studentList=getStudentList();
// 进行成绩排序-正序studentList.sort(Comparator.comparingDouble(Student::getScore));
// 排序-倒序studentList.sort(Comparator.comparingDouble(Student::getScore).reversed());

#排序优秀学生，使用了Boolean中的compare，而非比较器studentList.sort((o1, o2) ->Boolean.compare(o1.getMerit(), o2.getMerit()));
#排序学生名称-倒序，使用了通用的比较Comparator.comparingstudentList.sort(Comparator.comparing(Student::getName).reversed());

studentList.sort(Comparator.comparingInt(Student::getAge).thenComparing(Comparator.comparingDouble(Student::getScore).reversed()));
#注意，下面这种跟上面是不同的结果，注意studentList.sort(Comparator.comparingInt(Student::getAge).thenComparingDouble(Student::getScore).reversed());

// 排到最后studentList.sort(Comparator.comparing(Student::getScore, Comparator.nullsLast(Double::compareTo)));
// 排到最前studentList.sort(Comparator.comparing(Student::getScore, Comparator.nullsFirst(Double::compareTo)));

// 排到最后studentList.sort(Comparator.nullsLast(Comparator.comparing(Student::getScore, Comparator.nullsFirst(Double::compareTo))));
// 排到最前studentList.sort(Comparator.nullsFirst(Comparator.comparing(Student::getScore, Comparator.nullsFirst(Double::compareTo))));